Intel Assemble Instruction Set

 

CONTENT



Intel 8086 Family Architecture
Instruction Clock Cycle Calculation
8088/8086  Effective Address (EA) Calculation
Task State Calculation
FLAGS - Intel 8086 Family Flags Register
MSW - Machine Status Word (286+ only)
8086/80186/80286/80386/80486 Instruction Set
     AAA - Ascii Adjust for Addition
     AAD - Ascii Adjust for Division
     AAM - Ascii Adjust for Multiplication
     AAS - Ascii Adjust for Subtraction
     ADC - Add With Carry
     ADD - Arithmetic Addition
     AND - Logical And
     ARPL - Adjusted Requested Privilege Level of Selector (286+ PM)
     BOUND - Array Index Bound Check (80188+)
     BSF - Bit Scan Forward (386+)
     BSR - Bit Scan Reverse  (386+)
     BSWAP - Byte Swap       (486+)
     BT - Bit Test           (386+)
     BTC - Bit Test with Compliment (386+)
     BTR - Bit Test with Reset (386+)
     BTS - Bit Test and Set  (386+)
     CALL - Procedure Call
     CBW - Convert Byte to Word
     CDQ - Convert Double to Quad (386+)
     CLC - Clear Carry
     CLD - Clear Direction Flag
     CLI - Clear Interrupt Flag (disable)
     CLTS - Clear Task Switched Flag (286+ privileged)
     CMC - Complement Carry Flag
     CMP - Compare
     CMPS - Compare String (Byte, Word or Doubleword)
     CMPXCHG - Compare and Exchange
     CWD - Convert Word to Doubleword
     CWDE - Convert Word to Extended Doubleword (386+)
     DAA - Decimal Adjust for Addition
     DAS - Decimal Adjust for Subtraction
     DEC - Decrement
     DIV - Divide
     ENTER - Make Stack Frame (80188+)
     ESC - Escape
     HLT - Halt CPU
     IDIV - Signed Integer Division
     IMUL - Signed Multiply
     IN - Input Byte or Word From Port
     INC - Increment
     INS - Input String from Port (80188+)
     INT - Interrupt
     INTO - Interrupt on Overflow
     INVD - Invalidate Cache  (486+)
     INVLPG - Invalidate Translation Look-Aside Buffer Entry (486+)
     IRET/IRETD - Interrupt Return
     Jxx - Jump Instructions Table
     JCXZ/JECXZ - Jump if Register (E)CX is Zero
     JMP - Unconditional Jump
     LAHF - Load Register AH From Flags
     LAR - Load Access Rights (286+ protected)
     LDS - Load Pointer Using DS
     LEA - Load Effective Address
     LEAVE - Restore Stack for Procedure Exit (80188+)
     LES - Load Pointer Using ES
     LFS - Load Pointer Using FS (386+)
     LGDT - Load Global Descriptor Table (286+ privileged)
     LIDT - Load Interrupt Descriptor Table (286+ privileged)
     LGS - Load Pointer Using GS (386+)
     LLDT - Load Local Descriptor Table (286+ privileged)
     LMSW - Load Machine Status Word (286+ privileged)
     LOCK - Lock Bus
     LODS - Load String (Byte, Word or Double)
     LOOP - Decrement CX and Loop if CX Not Zero
     LOOPE/LOOPZ - Loop While Equal / Loop While Zero
     LOOPNZ/LOOPNE - Loop While Not Zero / Loop While Not Equal
     LSL - Load Segment Limit (286+ protected)
     LSS - Load Pointer Using SS (386+)
     LTR - Load Task Register (286+ privileged)
     MOV - Move Byte or Word
     MOVS - Move String (Byte or Word)
     MOVSX - Move with Sign Extend (386+)
     MOVZX - Move with Zero Extend (386+)
     MUL - Unsigned Multiply
     NEG - Two's Complement Negation
     NOP - No Operation (90h)
     NOT - One's Compliment Negation (Logical NOT)
     OR - Inclusive Logical OR
     OUT - Output Data to Port
     OUTS - Output String to Port (80188+)
     POP - Pop Word off Stack
     POPA/POPAD - Pop All Registers onto Stack (80188+)
     POPF/POPFD - Pop Flags off Stack
     PUSH - Push Word onto Stack
     PUSHA/PUSHAD - Push All Registers onto Stack (80188+)
     PUSHF/PUSHFD - Push Flags onto Stack
     RCL - Rotate Through Carry Left
     RCR - Rotate Through Carry Right
     REP - Repeat String Operation
     REPE/REPZ - Repeat Equal / Repeat Zero
     REPNE/REPNZ - Repeat Not Equal / Repeat Not Zero
     RET/RETF - Return From Procedure
     ROL - Rotate Left
     ROR - Rotate Right
     SAHF - Store AH Register into FLAGS
     SAL/SHL - Shift Arithmetic Left / Shift Logical Left
     SAR - Shift Arithmetic Right
     SBB - Subtract with Borrow/Carry
     SCAS - Scan String  (Byte, Word or Doubleword)
     SETAE/SETNB - Set if Above or Equal / Set if Not Below (386+)
     SETB/SETNAE - Set if Below / Set if Not Above or Equal (386+)
     SETBE/SETNA - Set if Below or Equal / Set if Not Above (386+)
     SETE/SETZ - Set if Equal / Set if Zero (386+)
     SETNE/SETNZ - Set if Not Equal / Set if Not Zero (386+)
     SETL/SETNGE - Set if Less / Set if Not Greater or Equal (386+)
     SETGE/SETNL - Set if Greater or Equal / Set if Not Less (386+)
     SETLE/SETNG - Set if Less or Equal / Set if Not greater or Equal (386+)
     SETG/SETNLE - Set if Greater / Set if Not Less or Equal (386+)
     SETS - Set if Signed (386+)
     SETNS - Set if Not Signed (386+)
     SETC - Set if Carry (386+)
     SETNC - Set if Not Carry (386+)
     SETO - Set if Overflow (386+)
     SETNO - Set if Not Overflow (386+)
     SETP/SETPE - Set if Parity / Set if Parity Even  (386+)
     SETNP/SETPO - Set if No Parity / Set if Parity Odd (386+)
     SGDT - Store Global Descriptor Table (286+ privileged)
     SIDT - Store Interrupt Descriptor Table (286+ privileged)
     SHL - Shift Logical Left
     SHR - Shift Logical Right
     SHLD/SHRD - Double Precision Shift (386+)
     SLDT - Store Local Descriptor Table (286+ privileged)
     SMSW - Store Machine Status Word (286+ privileged)
     STC - Set Carry
     STD - Set Direction Flag
     STI - Set Interrupt Flag  (Enable Interrupts)
     STOS - Store String  (Byte, Word or Doubleword)
     STR - Store Task Register (286+ privileged)
     SUB - Subtract
     TEST - Test For Bit Pattern
     VERR - Verify Read (286+ protected)
     VERW - Verify Write (286+ protected)
     WAIT/FWAIT - Event Wait
     WBINVD - Write-Back and Invalidate Cache (486+)
     XCHG - Exchange
     XLAT/XLATB - Translate
     XOR - Exclusive OR

TEXT



Intel 8086 Family Architecture

        General Purpose Registers               Segment Registers

        AH/AL  AX  (EAX)  Accumulator            CS     Code Segment
        BH/BL  BX  (EBX)  Base                   DS     Data Segment
        CH/CL  CX  (ECX)  Counter                SS     Stack Segment
        DH/DL  DX  (EDX)  Data                   ES     Extra Segment
                                                (FS)    386 and newer
        (Exx) indicates 386+ 32 bit register    (GS)    386 and newer


        Pointer Registers                       Stack Registers

        SI (ESI)  Source Index                  SP (ESP)  Stack Pointer
        DI (EDI)  Destination Index             BP (EBP)  Base Pointer
        IP        Instruction Pointer


        Status Registers

        FLAGS Status Flags   (see FLAGS)

        Special Registers (386+ only)

        CR0     Control Register 0        DR0    Debug Register 0
        CR2     Control Register 2        DR1    Debug Register 1
        CR3     Control Register 3        DR2    Debug Register 2
                                          DR3    Debug Register 3
        TR4     Test Register 4           DR6    Debug Register 6
        TR5     Test Register 5           DR7    Debug Register 7
        TR6     Test Register 6
        TR7     Test Register 7
        
        Register          Default Segment    Valid Overrides

        BP                      SS              DS, ES, CS
        SI or DI                DS              ES, SS, CS
        DI strings              ES              None
        SI strings              DS              ES, SS, CS

        - see  CPU   DETECTING  Instruction Timing


Instruction Clock Cycle Calculation

        Some instructions require additional clock cycles due to a "Next
        Instruction Component" identified by a "+m" in the instruction
        clock cycle listings.  This is due to the prefetch queue being
        purge on a control transfers.   Below is the general rule for
        calculating "m":


        88/86 not applicable
        286  "m" is the number of bytes in the next instruction
        386  "m" is the number of components in the next instruction
                (the instruction coding (each byte), plus the data and
                the displacement are all considered components)


8088/8086  Effective Address (EA) Calculation

                   Description                            Clock Cycles

        Displacement                                            6
        Base or Index (BX,BP,SI,DI)                             5
        Displacement+(Base or Index)                            9
        Base+Index (BP+DI,BX+SI)                                7
        Base+Index (BP+SI,BX+DI)                                8
        Base+Index+Displacement (BP+DI,BX+SI)                  11
        Base+Index+Displacement (BP+SI+disp,BX+DI+disp)        12


        - add 4 cycles for word operands at odd addresses
        - add 2 cycles for segment override
        - 80188/80186 timings differ from those of the 8088/8086/80286


Task State Calculation

        "TS" is defined as switching from VM/486 or 80286 TSS to one of
        the following:

                        +---------------------------------------+
                        |               New Task                |
                        +-------+-------+-------+-------+-------+
        +---------------+486 TSS|486 TSS|386 TSS|386 TSS|286 TSS|
        |   Old Task    | (VM=0)| (VM=1)| (VM=0)| (VM=1)|       |
        +---------------+-------+-------+-------+-------+-------+
        386 TSS (VM=0)  |       |       |  309  |  226  |  282  |
                        +-------+-------+-------+-------+-------+
        386 TSS (VM=1)  |       |       |  314  |  231  |  287  |
                        +-------+-------+-------+-------+-------+
        386 CPU/286 TSS |       |       |  307  |  224  |  280  |
                        +-------+-------+-------+-------+-------+
        486 CPU/286 TSS |  199  |  177  |       |       |  180  |
                        +---------------------------------------+

                             
        Miscellaneous

        - all timings are for best case and do not take into account wait
          states, instruction alignment, the state of the prefetch queue,
          DMA refresh cycles, cache hits/misses or exception processing.
        - to convert clocks to nanoseconds divide one microsecond by the
          processor speed in MegaHertz:
   
          (1000MHz/(n MHz)) = X nanoseconds

        - see   8086 Architecture


FLAGS - Intel 8086 Family Flags Register

      |11|10|F|E|D|C|B|A|9|8|7|6|5|4|3|2|1|0|
        |  | | | | | | | | | | | | | | | | +---  CF Carry Flag
        |  | | | | | | | | | | | | | | | +---  1
        |  | | | | | | | | | | | | | | +---  PF Parity Flag
        |  | | | | | | | | | | | | | +---  0
        |  | | | | | | | | | | | | +---  AF Auxiliary Flag
        |  | | | | | | | | | | | +---  0
        |  | | | | | | | | | | +---  ZF Zero Flag
        |  | | | | | | | | | +---  SF Sign Flag
        |  | | | | | | | | +---  TF Trap Flag  (Single Step)
        |  | | | | | | | +---  IF Interrupt Flag
        |  | | | | | | +---  DF Direction Flag
        |  | | | | | +---  OF Overflow flag
        |  | | | +-----  IOPL I/O Privilege Level  (286+ only)
        |  | | +-----  NT Nested Task Flag  (286+ only)
        |  | +-----  0
        |  +-----  RF Resume Flag (386+ only)
        +------  VM  Virtual Mode Flag (386+ only)

        - see   PUSHF  POPF  STI  CLI  STD  CLD


MSW - Machine Status Word (286+ only)

      |31|30-5|4|3|2|1|0|  Machine Status Word
        |   |  | | | | +---- Protection Enable (PE)
        |   |  | | | +----- Math Present (MP)
        |   |  | | +------ Emulation (EM)
        |   |  | +------- Task Switched (TS)
        |   |  +-------- Extension Type (ET)
        |   +---------- Reserved
        +------------- Paging (PG)


        Bit 0   PE      Protection Enable, switches processor between
                        protected and real mode
        Bit 1   MP      Math Present, controls function of the WAIT
                        instruction
        Bit 2   EM      Emulation, indicates whether coprocessor functions
                        are to be emulated
        Bit 3   TS      Task Switched, set and interrogated by coprocessor
                        on task switches and when interpretting coprocessor
                        instructions
        Bit 4   ET      Extension Type, indicates type of coprocessor in
                        system
        Bits 5-30       Reserved
        bit 31  PG      Paging, indicates whether the processor uses page
                        tables to translate linear addresses to physical
                        addresses

        - see   SMSW  LMSW


8086/80186/80286/80386/80486 Instruction Set

AAA - Ascii Adjust for Addition

        Usage:  AAA
        Modifies flags: AF CF (OF,PF,SF,ZF undefined)

        Changes contents of AL to valid unpacked decimal.  The high order
        nibble is zeroed.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              8     3     4     3             1


AAD - Ascii Adjust for Division

        Usage:  AAD
        Modifies flags: SF ZF PF (AF,CF,OF undefined)

        Used before dividing unpacked decimal numbers.   Multiplies AH by
        10 and the adds result into AL.  Sets AH to zero.  This instruction
        is also known to have an undocumented behavior.

        AL := 10*AH+AL
        AH := 0

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              60    14    19    14            2


AAM - Ascii Adjust for Multiplication

        Usage:  AAM
        Modifies flags: PF SF ZF (AF,CF,OF undefined)

        AH := AL / 10
        AL := AL mod 10

        Used after multiplication of two unpacked decimal numbers, this
        instruction adjusts an unpacked decimal number.  The high order
        nibble of each byte must be zeroed before using this instruction.
        This instruction is also known to have an undocumented behavior.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              83    16    17    15            2


AAS - Ascii Adjust for Subtraction

        Usage:  AAS
        Modifies flags: AF CF (OF,PF,SF,ZF undefined)

        Corrects result of a previous unpacked decimal subtraction in AL.
        High order nibble is zeroed.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              8     3     4     3             1
        
        
ADC - Add With Carry

        Usage:  ADC     dest,src
        Modifies flags: AF CF OF SF PF ZF

        Sums two binary operands placing the result in the destination.
        If CF is set, a 1 is added to the destination.

                                Clocks                  Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     2     1             2
        mem,reg         16+EA   7     7     3            2-4  (W88=24+EA)
        reg,mem          9+EA   7     6     2            2-4  (W88=13+EA)
        reg,immed         4     3     2     1            3-4
        mem,immed       17+EA   7     7     3            3-6  (W88=23+EA)
        accum,immed       4     3     2     1            2-3


ADD - Arithmetic Addition

        Usage:  ADD     dest,src
        Modifies flags: AF CF OF PF SF ZF

        Adds "src" to "dest" and replacing the original contents of "dest".
        Both operands are binary.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     2     1             2
        mem,reg         16+EA   7     7     3            2-4  (W88=24+EA)
        reg,mem          9+EA   7     6     2            2-4  (W88=13+EA)
        reg,immed         4     3     2     1            3-4
        mem,immed       17+EA   7     7     3            3-6  (W88=23+EA)
        accum,immed       4     3     2     1            2-3


AND - Logical And

        Usage:  AND     dest,src
        Modifies flags: CF OF PF SF ZF (AF undefined)

        Performs a logical AND of the two operands replacing the destination
        with the result.

                                Clocks                  Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     2     1             2
        mem,reg         16+EA   7     7     3            2-4  (W88=24+EA)
        reg,mem          9+EA   7     6     1            2-4  (W88=13+EA)
        reg,immed         4     3     2     1            3-4
        mem,immed       17+EA   7     7     3            3-6  (W88=23+EA)
        accum,immed       4     3     2     1            2-3


ARPL - Adjusted Requested Privilege Level of Selector (286+ PM)

        Usage:  ARPL    dest,src
        (286+ protected mode)
        Modifies flags: ZF

        Compares the RPL bits of "dest" against "src".  If the RPL bits
        of "dest" are less than "src", the destination RPL bits are set
        equal to the source RPL bits and the Zero Flag is set.  Otherwise
        the Zero Flag is cleared.

                                Clocks                  Size
        Operands         808x  286   386   486          Bytes

        reg,reg           -     10    20    9             2
        mem,reg           -     11    21    9             4
        
BOUND - Array Index Bound Check (80188+)

        Usage:  BOUND   src,limit
        Modifies flags: None

        Array index in source register is checked against upper and lower
        bounds in memory source.  The first word located at "limit" is
        the lower boundary and the word at "limit+2" is the upper array bound.
        Interrupt 5 occurs if the source value is less than or higher than
        the source.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16,mem32       -   nj=13 nj=10   7             2
        reg32,mem64       -   nj=13 nj=10   7             2

        - nj = no jump taken


BSF - Bit Scan Forward (386+)

        Usage:  BSF     dest,src
        Modifies flags: ZF

        Scans source operand for first bit set.  Sets ZF if a bit is found
        set and loads the destination with an index to first set bit.  Clears
        ZF is no bits are found set.  BSF scans forward across bit pattern
        (0-n) while BSR scans in reverse (n-0).

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           -     -   10+3n  6-42           3
        reg,mem           -     -   10+3n  7-43          3-7
        reg32,reg32       -     -   10+3n  6-42          3-7
        reg32,mem32       -     -   10+3n  7-43          3-7


BSR - Bit Scan Reverse  (386+)

        Usage:  BSR     dest,src
        Modifies flags: ZF

        Scans source operand for first bit set.  Sets ZF if a bit is found
        set and loads the destination with an index to first set bit.  Clears
        ZF is no bits are found set.  BSF scans forward across bit pattern
        (0-n) while BSR scans in reverse (n-0).

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           -     -   10+3n  6-103          3
        reg,mem           -     -   10+3n  7-104         3-7
        reg32,reg32       -     -   10+3n  6-103         3-7
        reg32,mem32       -     -   10+3n  7-104         3-7


BSWAP - Byte Swap       (486+)

        Usage:  BSWAP   reg32
        Modifies flags: none

        Changes the byte order of a 32 bit register from big endian to
        little endian or vice versa.   Result left in destination register
        is undefined if the operand is a 16 bit register.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg32             -     -     -     1             2


BT - Bit Test           (386+)

        Usage:  BT      dest,src
        Modifies flags: CF

        The destination bit indexed by the source value is copied into the
        Carry Flag.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16,immed8      -     -     3     3            4-8
        mem16,immed8      -     -     6     6            4-8
        reg16,reg16       -     -     3     3            3-7
        mem16,reg16       -     -     12    12           3-7


BTC - Bit Test with Compliment (386+)

        Usage:  BTC     dest,src
        Modifies flags: CF

        The destination bit indexed by the source value is copied into the
        Carry Flag after being complimented (inverted).

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16,immed8      -     -     6     6            4-8
        mem16,immed8      -     -     8     8            4-8
        reg16,reg16       -     -     6     6            3-7
        mem16,reg16       -     -     13    13           3-7


BTR - Bit Test with Reset (386+)

        Usage:  BTR     dest,src
        Modifies flags: CF

        The destination bit indexed by the source value is copied into the
        Carry Flag and then cleared in the destination.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16,immed8      -     -     6     6            4-8
        mem16,immed8      -     -     8     8            4-8
        reg16,reg16       -     -     6     6            3-7
        mem16,reg16       -     -     13    13           3-7


BTS - Bit Test and Set  (386+)

        Usage:  BTS     dest,src
        Modifies flags: CF

        The destination bit indexed by the source value is copied into the
        Carry Flag and then set in the destination.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16,immed8      -     -     6     6            4-8
        mem16,immed8      -     -     8     8            4-8
        reg16,reg16       -     -     6     6            3-7
        mem16,reg16       -     -     13    13           3-7


CALL - Procedure Call

        Usage:  CALL    destination
        Modifies flags: None

        Pushes Instruction Pointer (and Code Segment for far calls) onto
        stack and loads Instruction Pointer with the address of proc-name.
        Code continues with execution at CS:IP.

                                                         Clocks
                   Operands                     808x   286     386     486

        rel16 (near, IP relative)                19     7      7+m      3
        rel32 (near, IP relative)                -      -      7+m      3

        reg16 (near, register indirect)          16     7      7+m      5
        reg32 (near, register indirect)          -      -      7+m      5

        mem16 (near, memory indirect)          21+EA    11    10+m      5
        mem32 (near, memory indirect)            -      -     10+m      5

        ptr16:16 (far, full ptr supplied)        28     13    17+m      18
        ptr16:32 (far, full ptr supplied)        -      -     17+m      18
        ptr16:16 (far, ptr supplied, prot. mode) -      26    34+m      20
        ptr16:32 (far, ptr supplied, prot. mode) -      -     34+m      20
        m16:16 (far, indirect)                 37+EA    16    22+m      17
        m16:32 (far, indirect)                   -      -     22+m      17
        m16:16 (far, indirect, prot. mode)       -      29    38+m      20
        m16:32 (far, indirect, prot. mode)       -      -     38+m      20

        ptr16:16 (task, via TSS or task gate)    -     177     TS     37+TS
        m16:16 (task, via TSS or task gate)      -   180/185  5+TS    37+TS
        m16:32 (task)                            -      -      TS     37+TS
        m16:32 (task)                            -      -     5+TS    37+TS

        ptr16:16 (gate, same privilege)          -      41    52+m      35
        ptr16:32 (gate, same privilege)          -      -     52+m      35
        m16:16 (gate, same privilege)            -      44    56+m      35
        m16:32 (gate, same privilege)            -      -     56+m      35

        ptr16:16 (gate, more priv, no parm)      -      82    86+m      69
        ptr16:32 (gate, more priv, no parm)      -      -     86+m      69
        m16:16 (gate, more priv, no parm)        -      83    90+m      69
        m16:32 (gate, more priv, no parm)        -      -     90+m      69

        ptr16:16 (gate, more priv, x parms)      -    86+4x  94+4x+m  77+4x
        ptr16:32 (gate, more priv, x parms)      -      -    94+4x+m  77+4x
        m16:16 (gate, more priv, x parms)        -    90+4x  98+4x+m  77+4x
        m16:32 (gate, more priv, x parms)        -      -    98+4x+m  77+4x


CBW - Convert Byte to Word

        Usage:  CBW
        Modifies flags: None

        Converts byte in AL to word Value in AX by extending sign of AL
        throughout register AH.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     3     3             1


CDQ - Convert Double to Quad (386+)

        Usage:  CDQ
        Modifies flags: None

        Converts signed DWORD in EAX to a signed quad word in EDX:EAX by
        extending the high order bit of EAX throughout EDX

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              -     -     2     3             1


CLC - Clear Carry

        Usage:  CLC
        Modifies flags: CF

        Clears the Carry Flag.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2     2             1


CLD - Clear Direction Flag

        Usage:  CLD
        Modifies flags: DF

        Clears the Direction Flag causing string instructions to increment
        the SI and DI index registers.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2     2             1


CLI - Clear Interrupt Flag (disable)

        Usage:  CLI
        Modifies flags: IF

        Disables the maskable hardware interrupts by clearing the Interrupt
        flag.  NMI's and software interrupts are not inhibited.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     3     5             1


CLTS - Clear Task Switched Flag (286+ privileged)

        Usage:  CLTS
        Modifies flags: None

        Clears the Task Switched Flag in the Machine Status Register.  This
        is a privileged operation and is generally used only by operating
        system code.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              -     2     5     7             2


CMC - Complement Carry Flag

        Usage:  CMC
        Modifies flags: CF

        Toggles (inverts) the Carry Flag

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2     2             1


CMP - Compare

        Usage:  CMP     dest,src
        Modifies flags: AF CF OF PF SF ZF

        Subtracts source from destination and updates the flags but does
        not save result.  Flags can subsequently be checked for conditions.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     2     1             2
        mem,reg          9+EA   7     5     2            2-4  (W88=13+EA)
        reg,mem          9+EA   6     6     2            2-4  (W88=13+EA)
        reg,immed         4     3     2     1            3-4
        mem,immed       10+EA   6     5     2            3-6  (W88=14+EA)
        accum,immed       4     3     2     1            2-3


CMPS - Compare String (Byte, Word or Doubleword)

        Usage:  CMPS    dest,src
                CMPSB
                CMPSW
                CMPSD   (386+)
        Modifies flags: AF CF OF PF SF ZF

        Subtracts destination value from source without saving results.
        Updates flags based on the subtraction and  the index registers
        (E)SI and (E)DI are incremented or decremented depending on the
        state of the Direction Flag.  CMPSB inc/decrements the index
        registers by 1, CMPSW inc/decrements by 2, while CMPSD increments
        or decrements by 4.  The REP prefixes can be used to process
        entire data items.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        dest,src          22    8     10    8             1  (W88=30)


CMPXCHG - Compare and Exchange

        Usage:  CMPXCHG dest,src  (486+)
        Modifies flags: AF CF OF PF SF ZF

        Compares the accumulator (8-32 bits) with "dest".  If equal the
        "dest" is loaded with "src", otherwise the accumulator is loaded
        with "dest".

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           -     -     -     6             2
        mem,reg           -     -     -     7             2

        - add 3 clocks if the "mem,reg" comparison fails


CWD - Convert Word to Doubleword

        Usage:  CWD
        Modifies flags: None

        Extends sign of word in register AX throughout register DX forming
        a doubleword quantity in DX:AX.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              5     2     2     3             1


CWDE - Convert Word to Extended Doubleword (386+)

        Usage:  CWDE
        Modifies flags: None

        Converts a signed word in AX to a signed doubleword in EAX by
        extending the sign bit of AX throughout EAX.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              -     -     3     3             1


DAA - Decimal Adjust for Addition

        Usage:  DAA
        Modifies flags: AF CF PF SF ZF (OF undefined)

        Corrects result (in AL) of a previous BCD addition operation.
        Contents of AL are changed to a pair of packed decimal digits.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              4     3     4     2             1


DAS - Decimal Adjust for Subtraction

        Usage:  DAS
        Modifies flags: AF CF PF SF ZF (OF undefined)

        Corrects result (in AL) of a previous BCD subtraction operation.
        Contents of AL are changed to a pair of packed decimal digits.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              4     3     4     2             1


DEC - Decrement

        Usage:  DEC     dest
        Modifies flags: AF OF PF SF ZF

        Unsigned binary subtraction of one from the destination.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              3     2     2     1             2
        mem             15+EA   7     6     3            2-4
        reg16/32          3     2     2     1             1


DIV - Divide

        Usage:  DIV     src
        Modifies flags: (AF,CF,OF,PF,SF,ZF undefined)

        Unsigned binary division of accumulator by source.  If the source
        divisor is a byte value then AX is divided by "src" and the quotient
        is placed in AL and the remainder in AH.  If source operand is a word
        value, then DX:AX is divided by "src" and the quotient is stored in AX
        and the remainder in DX.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8             80-90  14    14    16            2
        reg16           144-162 22    22    24            2
        reg32              -    -     38    40            2
        mem8        (86-96)+EA  17    17    16           2-4
        mem16     (150-168)+EA  25    25    24           2-4  (W88=158-176+EA)
        mem32              -    -     41    40           2-4


ENTER - Make Stack Frame  (80188+)

        Usage:  ENTER   locals,level
        Modifies flags: None

        Modifies stack for entry to procedure for high level language.
        Operand "locals" specifies the amount of storage to be allocated
        on the stack.   "Level" specifies the nesting level of the routine.
        Paired with the LEAVE instruction, this is an efficient method of
        entry and exit to procedures.

                                     Clocks                     Size
        Operands         808x    286       386       486        Bytes

        immed16,0         -       11       10         14          4
        immed16,1         -       15       12         17          4
        immed16,immed8    -   12+4(n-1) 15+4(n-1)    17+3n        4


ESC - Escape

        Usage:  ESC     immed,src
        Modifies flags: None

        Provides access to the data bus for other resident processors.
        The CPU treats it as a NOP but places memory operand on bus.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        immed,reg         2   9-20    ?                   2
        immed,mem         2   9-20    ?                  2-4


HLT - Halt CPU

        Usage:   HLT
        Modifies flags: None

        Halts CPU until RESET line is activated, NMI or maskable interrupt
        received.  The CPU becomes dormant but retains the current CS:IP
        for later restart.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     5     4             1


IDIV - Signed Integer Division

        Usage:   IDIV   src
        Modifies flags: (AF,CF,OF,PF,SF,ZF undefined)

        Signed binary division of accumulator by source.  If source is a
        byte value, AX is divided by "src" and the quotient is stored in
        AL and the remainder in AH.  If source is a word value, DX:AX is
        divided by "src", and the quotient is stored in AL and the
        remainder in DX.
                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8          101-112   17    19    19            2
        reg16         165-184   25    27    27            2
        reg32            -      -     43    43            2
        mem8     (107-118)+EA   20    22    20           2-4
        mem16    (171-190)+EA   38    30    28           2-4  (W88=175-194)
        mem32            -      -     46    44           2-4


IMUL - Signed Multiply

        Usage:  IMUL    src
                IMUL    src,immed        (286+)
                IMUL    dest,src,immed8  (286+)
                IMUL    dest,src         (386+)
        Modifies flags: CF OF (AF,PF,SF,ZF undefined)

        Signed multiplication of accumulator by "src" with result placed
        in the accumulator.  If the source operand is a byte value, it
        is multiplied by AL and the result stored in AX.  If the source
        operand is a word value it is multiplied by AX and the result is
        stored in DX:AX.  Other variations of this instruction allow
        specification of source and destination registers as well as a
        third immediate factor.

                                  Clocks                Size
        Operands         808x   286   386   486         Bytes

        reg8             80-98   13   9-14  13-18         2
        reg16           128-154  21   9-22  13-26         2
        reg32              -     -    9-38  12-42         2
        mem8             86-104  16  12-17  13-18        2-4
        mem16           134-160  24  12-25  13-26        2-4
        mem32              -     -   12-41  13-42        2-4
        reg16,reg16        -     -    9-22  13-26        3-5
        reg32,reg32        -     -    9-38  13-42        3-5
        reg16,mem16        -     -   12-25  13-26        3-5
        reg32,mem32        -     -   12-41  13-42        3-5
        reg16,immed        -     21   9-22  13-26         3
        reg32,immed        -     21   9-38  13-42        3-6
        reg16,reg16,immed  -     2    9-22  13-26        3-6
        reg32,reg32,immed  -     21   9-38  13-42        3-6
        reg16,mem16,immed  -     24  12-25  13-26        3-6
        reg32,mem32,immed  -     24  12-41  13-42        3-6


IN - Input Byte or Word From Port

        Usage:  IN      accum,port
        Modifies flags: None

        A byte, word or dword is read from "port" and placed in AL, AX or
        EAX respectively.  If the port number is in the range of 0-255
        it can be specified as an immediate, otherwise the port number
        must be specified in DX.  Valid port ranges on the PC are 0-1024,
        though values through 65535 may be specified and recognized by
        third party vendors and PS/2's.

                                 Clocks                 Size
        Operands         808x  286   386    486         Bytes

        accum,immed8    10/14   5     12     14           2
        accum,immed8 (PM)            6/26  8/28/27        2
        accum,DX         8/12   5     13     14           1
        accum,DX (PM)                7/27  8/28/27        1

        - 386+ protected mode timings depend on privilege levels.

          first number is the timing if:    CPL ?IOPL
          second number is the timing if:   CPL > IOPL or in VM 86 mode (386)
                                            CPL ?IOPL  (486)
          third number is the timing when:    virtual mode on 486 processor
        - 486 virtual mode always requires 27 cycles


INC - Increment

        Usage:  INC     dest
        Modifies flags: AF OF PF SF ZF

        Adds one to destination unsigned binary operand.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              3     2     2     1             2
        reg16             3     2     2     1             1
        reg32             3     2     2     1             1
        mem             15+EA   7     6     3            2-4  (W88=23+EA)


INS - Input String from Port  (80188+)

        Usage:  INS     dest,port
                INSB
                INSW
                INSD    (386+)
        Modifies flags: None

        Loads data from port to the destination ES:(E)DI  (even if a
        destination operand is supplied).  (E)DI is adjusted by the size
        of the operand and increased if the Direction Flag is cleared and
        decreased if the Direction Flag is set.  For INSB, INSW, INSD no
        operands are allowed and the size is determined by the mnemonic.

                                 Clocks                 Size
        Operands         808x  286   386    486         Bytes

        dest,port         -     5     15     17           1
        dest,port (PM)    -     5    9/29 10/32/30        1
        none              -     5     15     17           1
        none (PM)         -     5    9/29 10/32/30        1

        - 386+ protected mode timings depend on privilege levels.

          first number is the timing if:    CPL ?IOPL
          second number is the timing if:   CPL > IOPL
          third number is the timing if:    virtual mode on 486 processor


INT - Interrupt

        Usage:  INT     num
        Modifies flags: TF IF

        Initiates a software interrupt by pushing the flags, clearing the
        Trap and Interrupt Flags, pushing CS followed by IP and loading
        CS:IP with the value found in the interrupt vector table.  Execution
        then begins at the location addressed by the new CS:IP

                                               Clocks           Size
            Operands                    808x  286   386   486   Bytes

 3 (constant)                          52/72  23+m   33    26     2
 3 (prot. mode, same priv.)              -    40+m   59    44     2       
 3 (prot. mode, more priv.)              -    78+m   99    71     2
 3 (from VM86 to PL 0)                   -     -    119    82     2
 3 (prot. mode via task gate)            -   167+m   TS  37+TS    2
 immed8                                51/71  23+m   37    30     1
 immed8 (prot. mode, same priv.)         -    40+m   59    44     1
 immed8 (prot. mode, more priv.)         -    78+m   99    71     1
 immed8 (from VM86 to PL 0)              -     -    119    86     1
 immed8 (prot. mode, via task gate)      -   167+m   TS  37+TS    1


INTO - Interrupt on Overflow

        Usage:  INTO
        Modifies flags: IF TF

        If the Overflow Flag is set this instruction generates an INT 4
        which causes the code addressed by 0000:0010 to be executed.

                                          Clocks           Size
        Operands                808x    286   386   486    Bytes

        none: jump             53/73   24+m    35    28      1
              no jump            4       3     3     3
        (prot. mode, same priv.) -       -     59    46      1
        (prot. mode, more priv.) -       -     99    73      1
        (from VM86 to PL 0)      -       -    119    84      1
        (prot. mode, via task gate)      -     TS  39+TS     1


INVD - Invalidate Cache  (486+)

        Usage:  INVD
        Modifies flags: none

        Flushes CPU internal cache.  Issues special function bus cycle
        which indicates to flush external caches.   Data in write-back
        external caches is lost.
        
                                  Clocks                Size
        Operands         808x   286   386   486         Bytes

        none              -      -     -     4            2


INVLPG - Invalidate Translation Look-Aside Buffer Entry (486+)

        Usage:  INVLPG
        Modifies flags: none

        Invalidates a single page table entry in the Translation
        Look-Aside Buffer.  Intel warns that this instruction may be
        implemented differently on future processors.
        
                                  Clocks                Size
        Operands         808x   286   386   486         Bytes

        none              -      -     -     12           2

        - timing is for TLB entry hit only.


IRET/IRETD - Interrupt Return

        Usage:  IRET
                IRETD  (386+)
        Modifies flags: AF CF DF IF PF SF TF ZF

        Returns control to point of interruption by popping IP, CS
        and then the Flags from the stack and continues execution at
        this location.  CPU exception interrupts will return to the
        instruction that cause the exception because the CS:IP placed
        on the stack during the interrupt is the address of the offending
        instruction.

                                         Clocks                 Size
            Operands            808x   286   386   486          Bytes

    iret                       32/44  17+m    22    15            1
    iret  (prot. mode)           -    31+m    38    15            1
    iret  (to less privilege)    -    55+m    82    36            1
    iret  (different task, NT=1) -   169+m    TS  TS+32           1
    iretd                        -      -   22/38   15            1
    iretd (to less privilege)    -      -     82    36            1
    iretd (to VM86 mode)         -      -     60    15            1
    iretd (different task, NT=1) -      -     TS  TS+32           1

    - 386 timings are listed as real-mode/protected-mode


Jxx - Jump Instructions Table

        Mnemonic              Meaning                    Jump Condition

          JA     Jump if Above                         CF=0 and ZF=0
          JAE    Jump if Above or Equal                CF=0
          JB     Jump if Below                         CF=1
          JBE    Jump if Below or Equal                CF=1 or ZF=1
          JC     Jump if Carry                         CF=1
          JCXZ   Jump if CX Zero                       CX=0
          JE     Jump if Equal                         ZF=1
          JG     Jump if Greater (signed)              ZF=0 and SF=OF
          JGE    Jump if Greater or Equal (signed)     SF=OF
          JL     Jump if Less (signed)                 SF != OF
          JLE    Jump if Less or Equal (signed)        ZF=1 or SF != OF
          JMP    Unconditional Jump                    unconditional
          JNA    Jump if Not Above                     CF=1 or ZF=1
          JNAE   Jump if Not Above or Equal            CF=1
          JNB    Jump if Not Below                     CF=0
          JNBE   Jump if Not Below or Equal            CF=0 and ZF=0
          JNC    Jump if Not Carry                     CF=0
          JNE    Jump if Not Equal                     ZF=0
          JNG    Jump if Not Greater (signed)          ZF=1 or SF != OF
          JNGE   Jump if Not Greater or Equal (signed) SF != OF
          JNL    Jump if Not Less (signed)             SF=OF
          JNLE   Jump if Not Less or Equal (signed)    ZF=0 and SF=OF
          JNO    Jump if Not Overflow (signed)         OF=0
          JNP    Jump if No Parity                     PF=0
          JNS    Jump if Not Signed (signed)           SF=0
          JNZ    Jump if Not Zero                      ZF=0
          JO     Jump if Overflow (signed)             OF=1
          JP     Jump if Parity                        PF=1
          JPE    Jump if Parity Even                   PF=1
          JPO    Jump if Parity Odd                    PF=0
          JS     Jump if Signed (signed)               SF=1
          JZ     Jump if Zero                          ZF=1

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        Jx: jump          16   7+m   7+m    3             2
            no jump        4    3     3     1
        Jx  near-label     -    -    7+m    3             4
            no jump        -    -     3     1

        - It's a good programming practice to organize code so the
          expected case is executed without a jump since the actual
          jump takes longer to execute than falling through the test.
        - see   JCXZ  and  JMP  for their respective timings


JCXZ/JECXZ - Jump if Register (E)CX is Zero

        Usage:  JCXZ    label
                JECXZ   label  (386+)
        Modifies flags: None

        Causes execution to branch to "label" if register CX is zero.  Uses
        unsigned comparision.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        label:  jump      18   8+m   9+m    8             2
                no jump    6    4     5     5


JMP - Unconditional Jump

        Usage:  JMP     target
        Modifies flags: None

        Unconditionally transfers control to "label".  Jumps by default
        are within -32768 to 32767 bytes from the instruction following
        the jump.  NEAR and SHORT jumps cause the IP to be updated while FAR
        jumps cause CS and IP to be updated.

                                                        Clocks
                   Operands                     808x  286    386   486

        rel8  (relative)                        15    7+m    7+m    3
        rel16 (relative)                        15    7+m    7+m    3
        rel32 (relative)                         -     -     7+m    3
        reg16 (near, register indirect)         11    7+m    7+m    5
        reg32 (near, register indirect)          -     -     7+m    5
        mem16 (near, mem indirect)             18+EA  11+m  10+m    5
        mem32 (near, mem indirect)             24+EA  15+m  10+m    5
        ptr16:16 (far, dword immed)              -     -    12+m    17
        ptr16:16 (far, PM dword immed)           -     -    27+m    19
        ptr16:16 (call gate, same priv.)         -    38+m  45+m    32
        ptr16:16 (via TSS)                       -   175+m   TS   42+TS
        ptr16:16 (via task gate)                 -   180+m   TS   43+TS
        mem16:16 (far, indirect)                 -     -    43+m    13
        mem16:16 (far, PM indirect)              -     -    31+m    18
        mem16:16 (call gate, same priv.)         -    41+m  49+m    31
        mem16:16 (via TSS)                       -   178+m  5+TS  41+TS
        mem16:16 (via task gate)                 -   183+m  5+TS  42+TS
        ptr16:32 (far, 6 byte immed)             -     -    12+m    13
        ptr16:32 (far, PM 6 byte immed)          -     -    27+m    18
        ptr16:32 (call gate, same priv.)         -     -    45+m    31
        ptr16:32 (via TSS)                       -     -     TS   42+TS
        ptr16:32 (via task state)                -     -     TS   43+TS
        m16:32 (far, address at dword)           -     -    43+m    13
        m16:32 (far, address at dword)           -     -    31+m    18
        m16:32 (call gate, same priv.)           -     -    49+m    31
        m16:32 (via TSS)                         -     -    5+TS  41+TS
        m16:32 (via task state)                  -     -    5+TS  42+TS


LAHF - Load Register AH From Flags

        Usage:  LAHF
        Modifies flags: None

        Copies bits 0-7 of the flags register into AH.  This includes flags
        AF, CF, PF, SF and ZF other bits are undefined.

        AH := SF ZF xx AF xx PF xx CF

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              4     2     2     3             1


LAR - Load Access Rights (286+ protected)

        Usage:  LAR     dest,src
        Modifies flags: ZF

        The high byte of the of the destination register is overwritten by
        the value of the access rights byte and the low order byte is zeroed
        depending on the selection in the source operand.  The Zero Flag is
        set if the load operation is successful.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16,reg16       -     14    15    11            3
        reg32,reg32       -     -     15    11            3
        reg16,mem16       -     16    16    11           3-7
        reg32,mem32       -     -     16    11           3-7


LDS - Load Pointer Using DS

        Usage:  LDS     dest,src
        Modifies flags: None

        Loads 32-bit pointer from memory source to destination register
        and DS.  The offset is placed in the destination register and the
        segment is placed in DS.  To use this instruction the word at the
        lower memory address must contain the offset and the word at the
        higher address must contain the segment.  This simplifies the loading
        of far pointers from the stack and the interrupt vector table.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16,mem32     16+EA   7     7     6            2-4
        reg,mem (PM)      -     -     22    12           5-7


LEA - Load Effective Address

        Usage:  LEA     dest,src
        Modifies flags: None

        Transfers offset address of "src" to the destination register.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,mem          2+EA   3     2     1            2-4

        - the MOV instruction can often save clock cycles when used in
          place of LEA on 8088 processors


LEAVE - Restore Stack for Procedure Exit (80188+)

        Usage:  LEAVE
        Modifies flags: None

        Releases the local variables created by the previous ENTER
        instruction by restoring SP and BP to their condition before
        the procedure stack frame was initialized.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              -     5     4     5             1


LES - Load Pointer Using ES

        Usage:  LES     dest,src
        Modifies flags: None

        Loads 32-bit pointer from memory source to destination register
        and ES.  The offset is placed in the destination register and the
        segment is placed in ES.  To use this instruction the word at the
        lower memory address must contain the offset and the word at the
        higher address must contain the segment.  This simplifies the loading
        of far pointers from the stack and the interrupt vector table.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,mem         16+EA   7     7     6            2-4  (W88=24+EA)
        reg,mem (PM)      -     -     22    12           5-7


LFS - Load Pointer Using FS (386+)

        Usage:  LFS     dest,src
        Modifies flags: None

        Loads 32-bit pointer from memory source to destination register
        and FS.  The offset is placed in the destination register and the
        segment is placed in FS.  To use this instruction the word at the
        lower memory address must contain the offset and the word at the
        higher address must contain the segment.  This simplifies the loading
        of far pointers from the stack and the interrupt vector table.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,mem           -     -     7     6            5-7
        reg,mem (PM)      -     -     22    12           5-7


LGDT - Load Global Descriptor Table (286+ privileged)

        Usage:  LGDT    src
        Modifies flags: None

        Loads a value from an operand into the Global Descriptor Table
        (GDT) register.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        mem64             -     11    11    11            5


LIDT - Load Interrupt Descriptor Table (286+ privileged)

        Usage:  LIDT    src
        Modifies flags: None

        Loads a value from an operand into the Interrupt Descriptor Table
        (IDT) register.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        mem64             -     12    11    11            5


LGS - Load Pointer Using GS (386+)

        Usage:  LGS     dest,src
        Modifies flags: None

        Loads 32-bit pointer from memory source to destination register
        and GS.  The offset is placed in the destination register and the
        segment is placed in GS.  To use this instruction the word at the
        lower memory address must contain the offset and the word at the
        higher address must contain the segment.  This simplifies the loading
        of far pointers from the stack and the interrupt vector table.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,mem           -     -     7     6            5-7
        reg,mem (PM)      -     -     22    12           5-7


LLDT - Load Local Descriptor Table (286+ privileged)

        Usage:  LLDT    src
        Modifies flags: None

        Loads a value from an operand into the Local Descriptor Table 
        Register (LDTR).

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             -     17    20    11            3
        mem16             -     19    24    11            5


LMSW - Load Machine Status Word (286+ privileged)

        Usage:  LMSW    src
        Modifies flags: None

        Loads the Machine Status Word (MSW) from data found at "src"

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             -     3     10    13            3
        mem16             -     6     13    13            5


LOCK - Lock Bus

        Usage:  LOCK
                LOCK: (386+ prefix)
        Modifies flags: None

        This instruction is a prefix that causes the CPU assert bus lock
        signal during the execution of the next instruction.  Used to
        avoid two processors from updating the same data location.  The
        286 always asserts lock during an XCHG with memory operands.  This
        should only be used to lock the bus prior to XCHG, MOV, IN and
        OUT instructions.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     0     0     1             1


LODS - Load String (Byte, Word or Double)

        Usage:  LODS    src
                LODSB
                LODSW
                LODSD  (386+)
        Modifies flags: None

        Transfers string element addressed by DS:SI (even if an operand is
        supplied) to the accumulator.   SI is incremented based on the size
        of the operand or based on the instruction used.  If the Direction
        Flag is set SI is decremented, if the Direction Flag is clear SI
        is incremented.  Use with REP prefixes.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        src             12/16   5     5     5             1


LOOP - Decrement CX and Loop if CX Not Zero

        Usage:  LOOP    label
        Modifies flags: None

        Decrements CX by 1 and transfers control to "label" if CX is not
        Zero.  The "label" operand must be within -128 or 127 bytes of the
        instruction following the loop instruction

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        label:  jump      18   8+m  11+m    6             2
                no jump    5    4     ?     2


LOOPE/LOOPZ - Loop While Equal / Loop While Zero

        Usage:  LOOPE   label
                LOOPZ   label
        Modifies flags: None

        Decrements CX by 1 (without modifying the flags) and transfers
        control to "label" if CX != 0 and the Zero Flag is set.  The
        "label" operand must be within -128 or 127 bytes of the instruction
        following the loop instruction.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        label:  jump      18   8+m  11+m    9             2
                no jump    5    4     ?     6


LOOPNZ/LOOPNE - Loop While Not Zero / Loop While Not Equal

        Usage:  LOOPNZ  label
                LOOPNE  label
        Modifies flags: None

        Decrements CX by 1 (without modifying the flags) and transfers
        control to "label" if CX != 0 and the Zero Flag is clear.  The
        "label" operand must be within -128 or 127 bytes of the instruction
        following the loop instruction.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        label:  jump      19   8+m  11+m    9             2
                no jump    5    4     ?     6


LSL - Load Segment Limit (286+ protected)

        Usage:  LSL     dest,src
        Modifies flags: ZF

        Loads the segment limit of a selector into the destination register
        if the selector is valid and visible at the current privilege level.
        If loading is successful the Zero Flag is set, otherwise it is
        cleared.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16,reg16       -     14  20/25   10            3
        reg32,reg32       -     -   20/25   10            3
        reg16,mem16       -     16  21/26   10            5
        reg32,mem32       -     -   21/26   10            5

        - 386 times are listed "byte granular" / "page granular"


LSS - Load Pointer Using SS (386+)

        Usage:  LSS     dest,src
        Modifies flags: None

        Loads 32-bit pointer from memory source to destination register
        and SS.  The offset is placed in the destination register and the
        segment is placed in SS.  To use this instruction the word at the
        lower memory address must contain the offset and the word at the
        higher address must contain the segment.  This simplifies the loading
        of far pointers from the stack and the interrupt vector table.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,mem           -     -     7     6            5-7
        reg,mem (PM)      -     -     22    12           5-7


LTR - Load Task Register (286+ privileged)

        Usage:  LTR     src
        Modifies flags: None

        Loads the current task register with the value specified in "src".

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             -     17    23    20            3
        mem16             -     19    27    20            5


MOV - Move Byte or Word

        Usage:  MOV     dest,src
        Modifies flags: None

        Copies byte or word from the source operand to the destination
        operand.  If the destination is SS interrupts are disabled except
        on early buggy 808x CPUs.  Some CPUs disable interrupts if the
        destination is any of the segment registers

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           2     2     2     1             2
        mem,reg          9+EA   3     2     1            2-4  (W88=13+EA)
        reg,mem          8+EA   5     4     1            2-4  (W88=12+EA)
        mem,immed       10+EA   3     2     1            3-6  (W88=14+EA)
        reg,immed         4     2     2     1            2-3
        mem,accum         10    3     2     1             3   (W88=14)
        accum,mem         10    5     4     1             3   (W88=14)
        segreg,reg16      2     2     2     3             2
        segreg,mem16     8+EA   5     5     9            2-4  (W88=12+EA)
        reg16,segreg      2     2     2     3             2
        mem16,segreg     9+EA   3     2     3            2-4  (W88=13+EA)
        reg32,CR0/CR2/CR3 -     -     6     4
        CR0,reg32         -     -     10    16
        CR2,reg32         -     -     4     4             3
        CR3,reg32         -     -     5     4             3
        reg32,DR0/DR1/DR2/DR3   -     22   10             3
        reg32,DR6/DR7     -     -     22   10             3
        DR0/DR1/DR2/DR3,reg32   -     22   11             3
        DR6/DR7,reg32     -     -     16   11             3
        reg32,TR6/TR7     -     -     12    4             3
        TR6/TR7,reg32     -     -     12    4             3
        reg32,TR3                           3
        TR3,reg32                           6

        - when the 386 special registers are used all operands are 32 bits


MOVS - Move String (Byte or Word)

        Usage:  MOVS    dest,src
                MOVSB
                MOVSW
                MOVSD  (386+)
        Modifies flags: None

        Copies data from addressed by DS:SI (even if operands are given) to
        the location ES:DI destination and updates SI and DI based on the
        size of the operand or instruction used.  SI and DI are incremented
        when the Direction Flag is cleared and decremented when the Direction
        Flag is Set.  Use with REP prefixes.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        dest,src          18    5     7     7             1   (W88=26)


MOVSX - Move with Sign Extend (386+)

        Usage:  MOVSX   dest,src
        Modifies flags: None

        Copies the value of the source operand to the destination register
        with the sign extended.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           -     -     3     3             3
        reg,mem           -     -     6     3            3-7


MOVZX - Move with Zero Extend (386+)

        Usage:  MOVZX   dest,src
        Modifies flags: None

        Copies the value of the source operand to the destination register
        with the zeroes extended.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           -     -     3     3             3
        reg,mem           -     -     6     3            3-7


MUL - Unsigned Multiply

        Usage:  MUL     src
        Modifies flags: CF OF (AF,PF,SF,ZF undefined)

        Unsigned multiply of the accumulator by the source.  If "src" is
        a byte value, then AL is used as the other multiplicand and the
        result is placed in AX.  If "src" is a word value, then AX is
        multiplied by "src" and DX:AX receives the result.  If "src" is
        a double word value, then EAX is multiplied by "src" and EDX:EAX
        receives the result.  The 386+ uses an early out algorithm which
        makes multiplying any size value in EAX as fast as in the 8 or 16
        bit registers.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8            70-77   13   9-14  13-18          2
        reg16          118-113  21   9-22  13-26          2
        reg32             -     -    9-38  13-42         2-4
        mem8        (76-83)+EA  16  12-17  13-18         2-4
        mem16     (124-139)+EA  24  12-25  13-26         2-4
        mem32             -     -   12-21  13-42         2-4


NEG - Two's Complement Negation

        Usage:  NEG     dest
        Modifies flags: AF CF OF PF SF ZF

        Subtracts the destination from 0 and saves the 2s complement of
        "dest" back into "dest".

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg               3     2     2     1             2
        mem             16+EA   7     6     3            2-4  (W88=24+EA)


NOP - No Operation (90h)

        Usage:  NOP
        Modifies flags: None

        This is a do nothing instruction.  It results in occupation of both
        space and time and is most useful for patching code segments.
        (This is the original XCHG AL,AL instruction)

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              3     3     3     1             1


NOT - One's Compliment Negation (Logical NOT)

        Usage:  NOT     dest
        Modifies flags: None

        Inverts the bits of the "dest" operand forming the 1s complement.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg               3     2     2     1             2
        mem             16+EA   7     6     3            2-4  (W88=24+EA)


OR - Inclusive Logical OR

        Usage:  OR      dest,src
        Modifies flags: CF OF PF SF ZF (AF undefined)

        Logical inclusive OR of the two operands returning the result in
        the destination.  Any bit set in either operand will be set in the
        destination.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     2     1             2
        mem,reg         16+EA   7     7     3            2-4  (W88=24+EA)
        reg,mem          9+EA   7     6     2            2-4  (W88=13+EA)
        reg,immed         4     3     2     1            3-4
        mem8,immed8     17+EA   7     7     3            3-6
        mem16,immed16   25+EA   7     7     3            3-6
        accum,immed       4     3     2     1            2-3


OUT - Output Data to Port

        Usage:  OUT     port,accum
        Modifies flags: None

        Transfers byte in AL,word in AX or dword in EAX to the specified
        hardware port address.  If the port number is in the range of 0-255
        it can be specified as an immediate.  If greater than 255 then the
        port number must be specified in DX.  Since the PC only decodes 10
        bits of the port address, values over 1023 can only be decoded by
        third party vendor equipment and also map to the port range 0-1023.

                                 Clocks                 Size
        Operands         808x  286   386    486         Bytes

        immed8,accum    10/14   3     10     16           2
        immed8,accum (PM) -     -    4/24 11/31/29        2
        DX,accum         8/12   3     11     16           1
        DX,accum (PM)     -     -    5/25 10/30/29        1

        - 386+ protected mode timings depend on privilege levels.

          first number is the timing when:    CPL  IOPL
          second number is the timing when:   CPL > IOPL
          third number is the timing when:    virtual mode on 486 processor


OUTS - Output String to Port  (80188+)

        Usage:  OUTS    port,src
                OUTSB
                OUTSW
                OUTSD   (386+)
        Modifies flags: None

        Transfers a byte, word or doubleword from "src" to the hardware
        port specified in DX.  For instructions with no operands the "src"
        is located at DS:SI and SI is incremented or decremented by the
        size of the operand or the size dictated by the instruction format.
        When the Direction Flag is set SI is decremented, when clear, SI is
        incremented.  If the port number is in the range of 0-255 it can
        be specified as an immediate.  If greater than 255 then the port
        number must be specified in DX.  Since the PC only decodes 10 bits
        of the port address, values over 1023 can only be decoded by third
        party vendor equipment and also map to the port range 0-1023.

                                 Clocks                 Size
        Operands         808x  286   386    486         Bytes

        port,src          -     5     14     17           1
        port,src (PM)     -     -    8/28 10/32/30        1

        - 386+ protected mode timings depend on privilege levels.

          first number is the timing when:    CPL  IOPL
          second number is the timing when:   CPL > IOPL
          third number is the timing when:    virtual mode on 486 processor


POP - Pop Word off Stack

        Usage:  POP     dest
        Modifies flags: None

        Transfers word at the current stack top (SS:SP) to the destination
        then increments SP by two to point to the new stack top.  CS is not
        a valid destination.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             8     5     4     4             1
        reg32             4     -     -     4             1
        segreg            8     5     7     3             1
        mem16           17+EA   5     5     6            2-4
        mem32             5     -     -     6            2-4


POPA/POPAD - Pop All Registers onto Stack  (80188+)

        Usage:  POPA
                POPAD  (386+)
        Modifies flags: None

        Pops the top 8 words off the stack into the 8 general purpose 16/32
        bit registers.   Registers are popped in the following order: (E)DI,
        (E)SI, (E)BP, (E)SP, (E)DX, (E)CX and (E)AX.  The (E)SP value popped
        from the stack is actually discarded.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              -     19    24    9             1


POPF/POPFD - Pop Flags off Stack

        Usage:  POPF
                POPFD  (386+)
        Modifies flags: all flags

        Pops word/doubleword from stack into the Flags Register and then
        increments SP by 2 (for POPF) or 4 (for POPFD).

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none             8/12   5     5     9             1  (W88=12)
        none  (PM)        -     -     5     6             1


PUSH - Push Word onto Stack

        Usage:  PUSH    src
                PUSH    immed   (80188+ only)
        Modifies flags: None

        Decrements SP by the size of the operand (two or four, byte values
        are sign extended) and transfers one word from source to the stack
        top (SS:SP).

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16           11/15   3     2     1             1
        reg32             -     -     2     1             1
        mem16           16+EA   5     5     4            2-4  (W88=24+EA)
        mem32             -     -     5     4            2-4
        segreg          10/14   3     2     3             1
        immed             -     3     2     1            2-3


PUSHA/PUSHAD - Push All Registers onto Stack  (80188+)

        Usage:  PUSHA
                PUSHAD  (386+)
        Modifies flags: None

        Pushes all general purpose registers onto the stack in the following
        order: (E)AX, (E)CX, (E)DX, (E)BX, (E)SP, (E)BP, (E)SI, (E)DI.  The
        value of SP is the value before the actual push of SP.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              -     19    24    11            1


PUSHF/PUSHFD - Push Flags onto Stack

        Usage:  PUSHF
                PUSHFD  (386+)
        Modifies flags: None

        Transfers the Flags Register onto the stack.  PUSHF saves a 16 bit
        value while PUSHFD saves a 32 bit value.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none            10/14   3     4     4             1
        none  (PM)        -     -     4     3             1


RCL - Rotate Through Carry Left

        Usage:  RCL     dest,count
        Modifies flags: CF OF

           +-+     +---------------+
        +-+|C|<+--+|7 <---------- 0|<-+
        |  +-+     +---------------+  |
        +-----------------------------+

        Rotates the bits in the destination to the left "count" times with
        all data pushed out the left side re-entering on the right.  The
        Carry Flag holds the last bit rotated out.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,1             2     2     9     3            2
        mem,1           15+EA   7     10    4           2-4  (W88=23+EA)
        reg,CL           8+4n  5+n    9    8-30          2
        mem,CL        20+EA+4n 8+n    10   9-31         2-4  (W88=28+EA+4n)
        reg,immed8        -    5+n     9   8-30          3
        mem,immed8        -    8+n    10   9-31         3-5


RCR - Rotate Through Carry Right

        Usage:  RCR     dest,count
        Modifies flags: CF OF

           +---------------+     +-+
        +->|7 +---------> 0|+--->|C|+-+
        |  +---------------+     +-+  |
        +-----------------------------+

        Rotates the bits in the destination to the right "count" times with
        all data pushed out the right side re-entering on the left.  The
        Carry Flag holds the last bit rotated out.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,1             2     2     9     3            2
        mem,1           15+EA   7     10    4           2-4   (W88=23+EA)
        reg,CL           8+4n  5+n    9    8-30          2
        mem,CL        20+EA+4n 8+n    10   9-31         2-4   (W88=28+EA+4n)
        reg,immed8        -    5+n    9    8-30          3
        mem,immed8        -    8+n    10   9-31         3-5


REP - Repeat String Operation

        Usage:  REP
        Modifies flags: None

        Repeats execution of string instructions while CX != 0.  After
        each string operation, CX is decremented and the Zero Flag is
        tested.  The combination of a repeat prefix and a segment override
        on CPU's before the 386 may result in errors if an interrupt occurs
        before CX=0.  The following code shows code that is susceptible to
        this and how to avoid it:

         again:  rep movs  byte ptr ES:[DI],ES:[SI]   ; vulnerable instr.
                     jcxz  next              ; continue if REP successful
                     loop  again             ; interrupt goofed count
         next:

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2                   1


REPE/REPZ - Repeat Equal / Repeat Zero

        Usage:  REPE
                REPZ
        Modifies flags: None

        Repeats execution of string instructions while CX != 0 and the Zero
        Flag is set.  CX is decremented and the Zero Flag tested after
        each string operation.   The combination of a repeat prefix and a
        segment override on processors other than the 386 may result in
        errors if an interrupt occurs before CX=0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2                   1


REPNE/REPNZ - Repeat Not Equal / Repeat Not Zero

        Usage:  REPNE
                REPNZ
        Modifies flags: None

        Repeats execution of string instructions while CX != 0 and the Zero
        Flag is clear.   CX is decremented and the Zero Flag tested after
        each string operation.   The combination of a repeat prefix and a
        segment override on processors other than the 386 may result in
        errors if an interrupt occurs before CX=0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2                   1


RET/RETF - Return From Procedure

        Usage:  RET     nBytes
                RETF    nBytes
                RETN    nBytes
        Modifies flags: None

        Transfers control from a procedure back to the instruction address
        saved on the stack.  "n bytes" is an optional number of bytes to
        release.  Far returns pop the IP followed by the CS, while near
        returns pop only the IP register.

                                 Clocks                 Size
        Operands         808x  286    386   486         Bytes

        retn            16/20  11+m  10+m    5            1
        retn immed      20/24  11+m  10+m    5            3
        retf            26/34  15+m  18+m    13           1
        retf (PM, same priv.)   -    32+m    18           1
        retf (PM, lesser priv.) -      68    33           1
        retf immed      25/33  15+m  18+m    14           3
        retf immed (PM, same priv.)  32+m    17           1
        retf immed (PM, lesser priv.)  68    33           1


ROL - Rotate Left

        Usage:  ROL     dest,count
        Modifies flags: CF OF

        +-+     +---------------+
        |C|<++-+|7 <---------- 0|<-+
        +-+  |  +---------------+  |
             +---------------------+

        Rotates the bits in the destination to the left "count" times with
        all data pushed out the left side re-entering on the right.  The
        Carry Flag will contain the value of the last bit rotated out.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,1             2     2     3     3             2
        mem,1           15+EA   7     7     4            2-4  (W88=23+EA)
        reg,CL           8+4n  5+n    3     3             2
        mem,CL        20+EA+4n 8+n    7     4            2-4  (W88=28+EA+4n)
        reg,immed8        -    5+n    3     2             3
        mem,immed8        -    8+n    7     4            3-5


ROR - Rotate Right

        Usage:  ROR     dest,count
        Modifies flags: CF OF

           +---------------+     +-+
        +->|7 +---------> 0|+-+->|C|   
        |  +---------------+  |  +-+   
        +---------------------+        

        Rotates the bits in the destination to the right "count" times with
        all data pushed out the right side re-entering on the left.  The
        Carry Flag will contain the value of the last bit rotated out.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,1             2     2     3     3             2
        mem,1           15+EA   7     7     4            2-4  (W88=23+EA)
        reg,CL           8+4n  5+n    3     3             2
        mem,CL        20+EA+4n 8+n    7     4            2-4  (W88=28+EA+4n)
        reg,immed8        -    5+n    3     2             3
        mem,immed8        -    8+n    7     4            3-5


SAHF - Store AH Register into FLAGS

        Usage:  SAHF
        Modifies flags: AF CF PF SF ZF

        Transfers bits 0-7 of AH into the Flags Register.  This includes
        AF, CF, PF, SF and ZF.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              4     2     3     2             1


SAL/SHL - Shift Arithmetic Left / Shift Logical Left

        Usage:  SAL     dest,count
                SHL     dest,count
        Modifies flags: CF OF PF SF ZF (AF undefined)

        +-+     +---------------+     +-+
        |C|<---+|7 <---------- 0|<---+|0|
        +-+     +---------------+     +-+

        Shifts the destination left by "count" bits with zeroes shifted
        in on right.  The Carry Flag contains the last bit shifted out.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,1             2     2     3     3            2
        mem,1           15+EA   7     7     4           2-4  (W88=23+EA)
        reg,CL           8+4n  5+n    3     3            2
        mem,CL        20+EA+4n 8+n    7     4           2-4  (W88=28+EA+4n)
        reg,immed8        -    5+n    3     2            3
        mem,immed8        -    8+n    7     4           3-5


SAR - Shift Arithmetic Right

        Usage:  SAR     dest,count
        Modifies flags: CF OF PF SF ZF (AF undefined)

           +---------------+     +-+
        +-+|7 ----------> 0|---+>|C|
        |  +---------------+     +-+
        +---^

        Shifts the destination right by "count" bits with the current sign
        bit replicated in the leftmost bit.  The Carry Flag contains the
        last bit shifted out.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,1             2     2     3     3             2
        mem,1           15+EA   7     7     4            2-4  (W88=23+EA)
        reg,CL           8+4n  5+n    3     3             2
        mem,CL        20+EA+4n 8+n    7     4            2-4  (W88=28+EA+4n)
        reg,immed8        -    5+n    3     2             3
        mem,immed8        -    8+n    7     4            3-5


SBB - Subtract with Borrow/Carry

        Usage:  SBB     dest,src
        Modifies flags: AF CF OF PF SF ZF

        Subtracts the source from the destination, and subtracts 1 extra if
        the Carry Flag is set.   Results are returned in "dest".

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     2     1             2
        mem,reg         16+EA   7     6     3            2-4  (W88=24+EA)
        reg,mem          9+EA   7     7     2            2-4  (W88=13+EA)
        reg,immed         4     3     2     1            3-4
        mem,immed       17+EA   7     7     3            3-6  (W88=25+EA)
        accum,immed       4     3     2     1            2-3


SCAS - Scan String  (Byte, Word or Doubleword)

        Usage:  SCAS    string
                SCASB
                SCASW
                SCASD   (386+)
        Modifies flags: AF CF OF PF SF ZF

        Compares value at ES:DI (even if operand is specified) from the
        accumulator and sets the flags similar to a subtraction.  DI is
        incremented/decremented based on the instruction format (or
        operand size) and the state of the Direction Flag.  Use with REP
        prefixes.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        string            15    7     7     6             1  (W88=19)


SETAE/SETNB - Set if Above or Equal / Set if Not Below (386+)

        Usage:  SETAE   dest
                SETNB   dest
        (unsigned, 386+)
        Modifies flags: none

        Sets the byte in the operand to 1 if the Carry Flag is clear
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETB/SETNAE - Set if Below / Set if Not Above or Equal (386+)

        Usage:  SETB    dest
                SETNAE  dest
        (unsigned, 386+)
        Modifies flags: none

        Sets the byte in the operand to 1 if the Carry Flag is set
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETBE/SETNA - Set if Below or Equal / Set if Not Above (386+)

        Usage:  SETBE   dest
                SETNA   dest
        (unsigned, 386+)
        Modifies flags: none

        Sets the byte in the operand to 1 if the Carry Flag or the Zero
        Flag is set, otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETE/SETZ - Set if Equal / Set if Zero (386+)

        Usage:  SETE    dest
                SETZ    dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Zero Flag is set,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETNE/SETNZ - Set if Not Equal / Set if Not Zero (386+)

        Usage:  SETNE   dest
                SETNZ   dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Zero Flag is clear,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETL/SETNGE - Set if Less / Set if Not Greater or Equal (386+)

        Usage:  SETL    dest
                SETNGE  dest
        (signed, 386+)
        Modifies flags: none

        Sets the byte in the operand to 1 if the Sign Flag is not equal
        to the Overflow Flag, otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETGE/SETNL - Set if Greater or Equal / Set if Not Less (386+)

        Usage:  SETGE   dest
                SETNL   dest
        (signed, 386+)
        Modifies flags: none

        Sets the byte in the operand to 1 if the Sign Flag equals the
        Overflow Flag, otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETLE/SETNG - Set if Less or Equal / Set if Not greater or Equal (386+)

        Usage:  SETLE   dest
                SETNG   dest
        (signed, 386+)
        Modifies flags: none

        Sets the byte in the operand to 1 if the Zero Flag is set or the
        Sign Flag is not equal to the Overflow Flag,  otherwise sets the
        operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETG/SETNLE - Set if Greater / Set if Not Less or Equal (386+)

        Usage:  SETG    dest
                SETNLE  dest
        (signed, 386+)
        Modifies flags: none

        Sets the byte in the operand to 1 if the Zero Flag is clear or the
        Sign Flag equals to the Overflow Flag,  otherwise sets the operand
        to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETS - Set if Signed (386+)

        Usage:  SETS    dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Sign Flag is set, otherwise
        sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETNS - Set if Not Signed (386+)

        Usage:  SETNS   dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Sign Flag is clear,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETC - Set if Carry (386+)

        Usage:  SETC    dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Carry Flag is set,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETNC - Set if Not Carry (386+)

        Usage:  SETNC   dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Carry Flag is clear,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETO - Set if Overflow (386+)

        Usage:  SETO    dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Overflow Flag is set,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETNO - Set if Not Overflow (386+)

        Usage:  SETNO   dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Overflow Flag is clear,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETP/SETPE - Set if Parity / Set if Parity Even  (386+)

        Usage:  SETP    dest
                SETPE   dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Parity Flag is set,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SETNP/SETPO - Set if No Parity / Set if Parity Odd (386+)

        Usage:  SETNP   dest
                SETPO   dest
        Modifies flags: none

        Sets the byte in the operand to 1 if the Parity Flag is clear,
        otherwise sets the operand to 0.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg8              -     -     4     3             3
        mem8              -     -     5     4             3


SGDT - Store Global Descriptor Table (286+ privileged)

        Usage:  SGDT    dest
        Modifies flags: none

        Stores the Global Descriptor Table (GDT) Register into the
        specified operand.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        mem64             -     11    9     10            5


SIDT - Store Interrupt Descriptor Table (286+ privileged)

        Usage:  SIDT    dest
        Modifies flags: none

        Stores the Interrupt Descriptor Table (IDT) Register into the
        specified operand.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        mem64             -     12    9     10            5


SHL - Shift Logical Left

        See: SAL


SHR - Shift Logical Right

        Usage:  SHR     dest,count
        Modifies flags: CF OF PF SF ZF (AF undefined)

        +-+     +---------------+     +-+
        |0|---+>|7 ----------> 0|---+>|C|
        +-+     +---------------+     +-+

        Shifts the destination right by "count" bits with zeroes shifted
        in on the left.  The Carry Flag contains the last bit shifted out.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,1             2     2     3                   2
        mem,1           15+EA   7     7                  2-4   (W88=23+EA)
        reg,CL           8+4n  5+n    3                   2
        mem,CL        20+EA+4n 8+n    7                  2-4   (W88=28+EA+4n)
        reg,immed8        -    5+n    3                   3
        mem,immed8        -    8+n    7                  3-5


SHLD/SHRD - Double Precision Shift (386+)

        Usage:  SHLD    dest,src,count
                SHRD    dest,src,count
        Modifies flags: CF PF SF ZF (OF,AF undefined)

        SHLD shifts "dest" to the left "count" times and the bit positions
        opened are filled with the most significant bits of "src".  SHRD
        shifts "dest" to the right "count" times and the bit positions
        opened are filled with the least significant bits of the second
        operand.  Only the 5 lower bits of "count" are used.

                                        Clocks                  Size
        Operands                808x  286   386   486           Bytes

        reg16,reg16,immed8       -     -     3     2              4
        reg32,reg32,immed8       -     -     3     2              4
        mem16,reg16,immed8       -     -     7     3              6
        mem32,reg32,immed8       -     -     7     3              6
        reg16,reg16,CL           -     -     3     3              3
        reg32,reg32,CL           -     -     3     3              3
        mem16,reg16,CL           -     -     7     4              5
        mem32,reg32,CL           -     -     7     4              5


SLDT - Store Local Descriptor Table (286+ privileged)

        Usage:  SLDT    dest
        Modifies flags: none

        Stores the Local Descriptor Table (LDT) Register into the
        specified operand.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             -     2     2     2             3
        mem16             -     2     2     3             5


SMSW - Store Machine Status Word (286+ privileged)

        Usage:  SMSW    dest
        Modifies flags: none

        Store Machine Status Word (MSW) into "dest".

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             -     2     10    2             3
        mem16             -     3     3     3             5


STC - Set Carry

        Usage:  STC
        Modifies flags: CF

        Sets the Carry Flag to 1.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2     2             1


STD - Set Direction Flag

        Usage:  STD
        Modifies flags: DF

        Sets the Direction Flag to 1 causing string instructions to
        auto-decrement SI and DI instead of auto-increment.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2     2             1


STI - Set Interrupt Flag  (Enable Interrupts)

        Usage:  STI
        Modifies flags: IF

        Sets the Interrupt Flag to 1, which enables recognition of all
        hardware interrupts.  If an interrupt is generated by a hardware
        device, an End of Interrupt (EOI) must also be issued to enable
        other hardware interrupts of the same or lower priority.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              2     2     2     5             1


STOS - Store String  (Byte, Word or Doubleword)

        Usage:  STOS    dest
                STOSB
                STOSW
                STOSD
        Modifies flags: None

        Stores value in accumulator to location at ES:(E)DI (even if operand
        is given).  (E)DI is incremented/decremented based on the size of
        the operand (or instruction format) and the state of the Direction
        Flag.   Use with REP prefixes.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        dest              11    3     4     5             1  (W88=15)


STR - Store Task Register (286+ privileged)

        Usage:  STR     dest
        Modifies flags: None

        Stores the current Task Register to the specified operand.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             -     2     2     2             3
        mem16             -     3     2     3             5


SUB - Subtract

        Usage:  SUB     dest,src
        Modifies flags: AF CF OF PF SF ZF

        The source is subtracted from the destination and the result is
        stored in the destination.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     2     1             2
        mem,reg         16+EA   7     6     3            2-4  (W88=24+EA)
        reg,mem          9+EA   7     7     2            2-4  (W88=13+EA)
        reg,immed         4     3     2     1            3-4
        mem,immed       17+EA   7     7     3            3-6  (W88=25+EA)
        accum,immed       4     3     2     1            2-3


TEST - Test For Bit Pattern

        Usage:  TEST    dest,src
        Modifies flags: CF OF PF SF ZF (AF undefined)

        Performs a logical AND of the two operands updating the flags
        register without saving the result.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     1     1             2
        reg,mem          9+EA   6     5     1            2-4  (W88=13+EA)
        mem,reg          9+EA   6     5     2            2-4  (W88=13+EA)
        reg,immed         5     3     2     1            3-4
        mem,immed       11+EA   6     5     2            3-6
        accum,immed       4     3     2     1            2-3


VERR - Verify Read (286+ protected)

        Usage:  VERR    src
        Modifies flags: ZF

        Verifies the specified segment selector is valid and is readable
        at the current privilege level.  If the segment is readable,
        the Zero Flag is set, otherwise it is cleared.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             -     14    10    11            3
        mem16             -     16    11    11            5


VERW - Verify Write (286+ protected)

        Usage:  VERW    src
        Modifies flags: ZF

        Verifies the specified segment selector is valid and is ratable
        at the current privilege level.  If the segment is writable,
        the Zero Flag is set, otherwise it is cleared.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg16             -     14    15    11            3
        mem16             -     16    16    11            5


WAIT/FWAIT - Event Wait

        Usage:  WAIT
                FWAIT
        Modifies flags: None

        CPU enters wait state until the coprocessor signals it has finished
        its operation.  This instruction is used to prevent the CPU from
        accessing memory that may be temporarily in use by the coprocessor.
        WAIT and FWAIT are identical.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              4     3     6+   1-3            1


WBINVD - Write-Back and Invalidate Cache (486+)

        Usage:  WBINVD
        Modifies flags: None

        Flushes internal cache, then signals the external cache to write
        back current data followed by a signal to flush the external cache.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        none              -     -     -     5             2


XCHG - Exchange

        Usage:  XCHG    dest,src
        Modifies flags: None

        Exchanges contents of source and destination.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           4     3     3     3             2
        mem,reg         17+EA   5     5     5            2-4  (W88=25+EA)
        reg,mem         17+EA   5     5     3            2-4  (W88=25+EA)
        accum,reg         3     3     3     3             1
        reg,accum         3     3     3     3             1


XLAT/XLATB - Translate

        Usage:  XLAT    translation-table
                XLATB   (masm 5.x)
        Modifies flags: None

        Replaces the byte in AL with byte from a user table addressed by
        BX.  The original value of AL is the index into the translate table.
        The best way to discripe this is MOV AL,[BX+AL]

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        table offset      11    5     5     4             1


XOR - Exclusive OR

        Usage:  XOR     dest,src
        Modifies flags: CF OF PF SF ZF (AF undefined)

        Performs a bitwise exclusive OR of the operands and returns
        the result in the destination.

                                 Clocks                 Size
        Operands         808x  286   386   486          Bytes

        reg,reg           3     2     2     1             2
        mem,reg         16+EA   7     6     3            2-4  (W88=24+EA)
        reg,mem          9+EA   7     7     2            2-4  (W88=13+EA)
        reg,immed         4     3     2     1            3-4
        mem,immed       17+EA   7     7     3            3-6  (W88=25+EA)
        accum,immed       4     3     2     1            2-3