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80x86 Integer Instruction Set (8088 - Pentium)

Legend:

General

acc AL, AX or EAX unless specified otherwise
reg any general register
r8 any 8-bit register
r16 any general purpose 16-bit register
r32 any general purpose 32-bit register
imm immediate data
imm8 8-bit immediate data
imm16 16-bit immediate data
mem memory address
mem8 address of 8-bit data item
mem16 address of 16-bit data item
mem32 address of 32-bit data item
mem48 address of 48-bit data item
dest 16/32-bit destination
short 8-bit destination

Integer instruction timings:

n generally refers to a number of repeated counts
m in a jump or call;
286: bytes in next instruction
386/486: number of components
(each byte of opcode) + 1 (if immed data) + 1 (if displacement) 
EA = cycles to calculate the Effective Address
       8088/8086:
        base   = 5   BP+DI or BX+SI = 7   BP+DI+disp or BX+SI+disp = 11
        index  = 5   BX+DI or BP+SI = 8   BX+DI+disp or BP+SI+disp = 12
        disp   = 6   segment override = +2
       286 - 486:
        base+index+disp = +1    all others, no penalty

instruction length:

The byte count includes the opcode length and length of any required displacement or immediate data. If the displacement is optional, it is shown as d() with the possible lengths in parentheses. If the immediate data is optional, it is shown as i() with the possible lengths in parentheses.

pairing categories for Pentium:

NP not pairable
UV pairable in the U pipe or V pipe
PU pairable in the U pipe only
PV pairable in the V pipe only

Instruction formats, clock cycles and Pentium® Pairing info

AAA

ASCII adjust after addition

operands bytes 8088 186 286 386 486 Pentium
- 1 8 8 3 4 3 3 NP

Example: 

        aaa

AAD

ASCII adjust AX before division (second byte is divisor)

operands bytes 8088 186 286 386 486 Pentium
- 2 60 15 14 19 14 10 NP

Example: 

        aad

AAM

ASCII adjust AX after multiply (second byte is divisor)

operands bytes 8088 186 286 386 486 Pentium
- 2 83 19 16 17 15 18 NP

Example: 

        aam

AAS

ASCII adjust AL after subtraction

operands bytes 8088 186 286 386 486 Pentium
- 1 8 7 3 4 3 3 NP

Example: 

        aas

ADC

Integer add with carry

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 3 3 2 2 1 1 PU
mem, reg 2+d(0,2) 24+EA 10 7 7 3 3 PU
reg, mem 2+d(0,2) 13+EA 10 7 6 2 2 PU
reg, imm 2+i(1,2) 4 4 3 2 1 1 PU
mem, imm 2+d(0,2)
+i(1,2) 		23+EA 16 7 7 3 3 PU*
acc, imm 1+i(1,2) 4 4 3 2 1 1 PU

* : not pairable if there is a displacement and immediate

Example: 

        adc     eax, ebx

ADD

Integer addition

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 3 3 2 2 1 1 UV
mem, reg 2+d(0,2) 24+EA 10 7 7 3 3 UV
reg, mem 2+d(0,2) 13+EA 10 7 6 2 2 UV
reg, imm 2+i(1,2) 4 4 3 2 1 1 UV
mem, imm 2+d(0,2)
+i(1,2) 		23+EA 16 7 7 3 3 UV*
acc, imm 1+i(1,2) 4 4 3 2 1 1 UV

* = not pairable if there is a displacement and immediate

Example: 

        add     eax, ebx

AND

Logical AND

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 3 3 2 2 1 1 UV
mem, reg 2+d(0,2) 24+EA 10 7 7 3 3 UV
reg, mem 2+d(0,2) 13+EA 10 7 6 2 2 UV
reg, imm 2+i(1,2) 4 4 3 2 1 1 UV
mem, imm 2+d(0,2)
+i(1,2) 		23+EA 16 7 7 3 3 UV*
acc, imm 1+i(1,2) 4 4 3 2 1 1 UV

* : not pairable if there is a displacement and immediate

Example: 

        and     eax, ebx

ARPL

Adjust RPL field of selector (286+)

operands bytes 286 386 486 Pentium
reg, reg 2 10 20 9 7 NP
mem, reg 2+d(0-2) 11 21 9 7 NP

Example: 

        arpl    ax, bx

BOUND

Check array index against bounds (186+)

operands bytes 186 286 386 486 Pentium
reg, mem 4 35 13 10 7 8 NP

Example: 

        bound   bx, array

BSF

Bit scan forward (386+)

operands bytes 386 486 Pentium
r16, r16 3 10+3n 6-42 6-34 NP
r32, r32 3 10+3n 6-42 6-42 NP
r16, m16 3+d(0,1,2) 10+3n 7-43 6-35 NP
r32, m32 3+d(0,1,2,4) 10+3n 7-43 6-43 NP

Example: 

        bsf     eax, [esi]

BSR

Bit scan reverse (386+)

operands bytes 386 486 Pentium
r16, r16 3 10+3n 6-103 7-39 NP
r32, r32 3 10+3n 7-104 7-71 NP
r16, m16 3+d(0,1,2) 10+3n 6-103 7-40 NP
r32, m32 3+d(0,1,2,4) 10+3n 7-104 7-72 NP

Example: 

        bsr     eax, [esi]

BSWAP

Byte swap (486+)

operand bytes 486 Pentium
r32 2 1 1 NP

Example: 

        bswap   eax

BT

Bit test (386+)

operands bytes 386 486 Pentium
reg, reg 3 3 3 4 NP
mem, reg 3+d(0,1,2,4) 12 8 9 NP
reg, imm8 3+i(1) 3 3 4 NP
mem, imm8 3+d(0,1,2,4)+i(1) 6 3 4 NP

Example: 

        bt      eax, 4

BTC

Bit test and complement (386+)

operands bytes 386 486 Pentium
reg, reg 3 6 6 7 NP
mem, reg 3+d(0,1,2,4) 13 13 13 NP
reg, imm8 3+i(1) 6 6 7 NP
mem, imm8 3+d(0,1,2,4)+i(1) 8 8 8 NP

Example: 

        btc     eax, 4

BTR

Bit test and reset (386+)

operands bytes 386 486 Pentium
reg, reg 3 6 6 7 NP
mem, reg 3+d(0,1,2,4) 13 13 13 NP
reg, imm8 3+i(1) 6 6 7 NP
mem, imm8 3+d(0,1,2,4)+i(1) 8 8 8 NP

Example: 

        btr     eax, 4

BTS

Bit test and set (386+)

operands bytes 386 486 Pentium
reg, reg 3 6 6 7 NP
mem, reg 3+d(0,1,2,4) 13 13 13 NP
reg, imm8 3+i(1) 6 6 7 NP
mem, imm8 3+d(0,1,2,4)+i(1) 8 8 8 NP

Example: 

        bts     eax, 4

CALL

Call subroutine

operand bytes 8088 186 286 386 486 Pentium
near 3 23 14 7+m 7+m 3 1 PV
reg 2 20 13 7+m 7+m 5 2 NP
mem16 2+d(0-2) 29+EA 19 11+m 10+m 5 2 NP
far 5 36 23 13+m 17+m 18 4 NP
mem32 2+d(0-2) 53+EA 38 16+m 22+m 17 4 NP

Protected Mode

operand bytes 286 386 486 Pentium
far 5 26+m 34+m 20 4-13 NP
mem32 2+d(0-2) 29+m 38+m 20 5-14 NP

cycles not shown for calls through call and task gates

Example: 

        call    my_function

CBW

Convert byte to word (AL –> AX)

operand bytes 8088 186 286 386 486 Pentium
- 1 2 2 2 3 3 3 NP

Example: 

        cbw

CWDE

Convert word to dword (386+) (AX –> EAX)

operand bytes 386 486 Pentium
- 1 3 3 3 NP

Example: 

        cwde

CWD

Convert word to double (AX –> DX:AX)

operand bytes 8088 186 286 386 486 Pentium
- 1 5 4 2 2 3 2 NP

Example: 

        cwd

CDQ

Convert double to quad (EAX –> EDX:EAX)

operand bytes 386 486 Pentium
- 1 2 3 2 NP

Example: 

        cdq

CLC

Clear the carry flag

operand bytes 8088 186 286 386 486 Pentium
- 1 2 2 2 2 2 2 NP

Example: 

        clc

CLD

Clear the direction flag (set to forward direction)

operand bytes 8088 186 286 386 486 Pentium
- 1 2 2 2 2 2 2 NP

Example: 

        cld

CLI

Clear the interrupt flag (disable interrupts)

operand bytes 8088 186 286 386 486 Pentium
- 1 2 2 3 3 5 7 NP

Example: 

        cli

CLTS

Clear task switched flag in CR0 (286+)

operand bytes 286 386 486 Pentium
- 2 2 5 7 10 NP

Example: 

        clts

CMC

Complement carry flag

operand bytes 8088 186 286 386 486 Pentium
- 1 2 2 2 2 2 2 NP

Example: 

        cmc

CMP

Compare two operands

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 3 3 2 2 1 1 UV
mem, reg 2+d(0,2) 13+EA 10 7 5 2 2 UV
reg, mem 2+d(0,2) 13+EA 10 6 6 2 2 UV
reg, imm 2+i(1,2) 4 4 3 2 1 1 UV
mem, imm 2+d(0,2)
+i(1,2) 		14+EA 10 6 5 2 2 UV*
acc, imm 1+i(1,2) 4 4 3 2 1 1 UV

* : not pairable if there is a displacement and immediate

Example: 

        cmp     eax, 3

CMPS/CMPSB/CMPSW/CMPSD

Compare string operands

variations bytes 8088 186 286 386 486 Pentium
cmpsb 1 30 22 8 10 8 5 NP
cmpsw 1 - - - 10 8 5 NP
cmpsd 1 - - - 10 8 5 NP
repX cmpsb 2 9+30n 5+22n 5+9n 5+9n 7+7n* 9+4n NP
repX cmpsw 2 9+30n 5+22n 5+9n 5+9n 7+7n* 9+4n NP
repX cmpsd 2 - - - 5+9n 7+7n* 9+4n NP

repX = repe, repz, repne or repnz

* : 5 if n = 0

Example: 

        repne cmpsb

CMPXCHG

Compare and Exchange (486+)

operands bytes 486 Pentium
reg, reg 3 6 5 NP
mem, reg 3+d(0-2) 7-10 6 NP

Example: 

        cmpxchg ebx, edx

CMPXCHG8B

Compare and Exchange 8 bytes (Pentium+)

operands bytes Pentium
mem, reg 3+d(0-2) 10 NP

Example: 

        cmpxchg8b [ebx], edx

CPUID

CPU identification (Pentium+)

operands bytes Pentium
- 2 14 NP

Example: 

        cpuid

DAA

Decimal adjust AL after addition

operand bytes 8088 186 286 386 486 Pentium
- 1 4 4 3 4 2 3 NP

Example: 

        daa

DAS

Decimal adjust AL after subtraction

operand bytes 8088 186 286 386 486 Pentium
- 1 4 4 3 4 2 3 NP

Example: 

        das

DEC

Decrement

operand bytes 8088 186 286 386 486 Pentium
r8 2 3 3 2 2 1 1 UV
r16 1 3 3 2 2 1 1 UV
r32 1 3 3 2 2 1 1 UV
mem 2+d(0,2) 23+EA 15 7 6 3 3 UV

Example: 

        dec     eax

DIV

Unsigned divide

operand bytes 8088 186 286 386 486 Pentium
r8 2 80-90 29 14 14 16 17 NP
r16 2 144-162 38 22 22 24 25 NP
r32 2 - - - 38 40 41 NP
mem8 2+d(0-2) 86-96+EA 35 17 17 16 17 NP
mem16 2+d(0-2) 150-168+EA 44 25 25 24 25 NP
mem32 2+d(0-2) - - - 41 40 41 NP
implied
dividend 		operand quotient remainder
AX / byte = AL AH
DX:AX / word = AX DX
EDX:EAX / dword = EAX EDX

Example: 

        div     ebx

ENTER

Make stack frame for procedure parameters (186+)

operands bytes 8088 186 286 386 486 Pentium
imm16, 0 3 - 15 11 10 14 11 NP
imm16, 1 4 - 25 15 12 17 15 NP
imm16, imm8 4 - 22+16n 12+4n 15+4n 17+3i 15+2i NP

Example: 

        enter   1, 0

ESC

Escape

escape opcodes D8 - DF are used by floating point instructions

HLT

Halt

operands bytes 8088 186 286 386 486 Pentium
- 1 2 2 2 5 4 4 NP

Example: 

        hlt

IDIV

Signed divide

operand bytes 8088 186 286 386 486 Pentium
r8 2 101-112 44-52 17 19 19 22 NP
r16 2 165-184 53-61 25 27 27 30 NP
r32 2 - - - 43 43 46 NP
mem8 2+d(0-2) 107-118+EA 50-58 20 22 20 22 NP
mem16 2+d(0-2) 171-190+EA 59-67 28 30 28 30 NP
mem32 2+d(0-2) - - - 46 44 46 NP
implied
dividend 		operand quotient remainder
AX byte AL AH
DX:AX word AX DX
EDX:EAX dword EAX EDX

Example: 

        idiv    ebx

IMUL

Signed multiply

Accumulator Multiplies

operand bytes 8088 186 286 386 486 Pentium
r8 2 80-98 25-28 13 9-14 13-18 11 NP
r16 2 128-154 34-37 21 9-22 13-26 11 NP
r32 2 - - - 9-38 13-42 10 NP
mem8 2+d(0-2) 86-104+EA 32-34 16 12-17 13-18 11 NP
mem16 2+d(0-2) 134-160+EA 40-43 24 12-25 13-26 11 NP
mem32 2+d(0-2) - - - 12-41 13-42 10 NP
implied
multiplicand 		operand
(multiplier) 		result
AL byte AX
AX word DX:AX
EAX dword EDX:EAX

Example: 

        imul    ebx

2 and 3 operand Multiplies

operands bytes 186 286 386 486 Pentium
r16, imm 2+i(1,2) - 21 9-14 / 9-22 13-18 / 13-26 10 NP
r32, imm 2+i(1,2) - - 9-38 13-42 10 NP
r16,r16,imm 2+i(1,2) 22/29 21 9-14 / 9-22 13-18 / 13-26 10 NP
r32,r32,imm 2+i(1,2) - - 9-38 13-42 10 NP
r16,m16,imm 2+d(0-2)
+i(1,2) 		25/32 24 12-17 / 12-25 13-18 / 13-26 10 NP
r32,m32,imm 2+d(0-2)+i (1,2) - 12-41 13-42 10 NP
r16, r16 2+i(1,2) - - 9-22 13-18 / 13-26 10 NP
r32, r32 2+i(1,2) - - 9-38 13-42 10 NP
r16, m16 2+d(0-2)+i (1,2) - 12-25 13-18 / 13-26 10 NP
r32, m32 2+d(0-2)+i (1,2) - 12-41 13-42 10 NP 
all forms: dest, src                          cycles for:   byte/word
               or                                             dword
           dest, src1, src2

Example: 

        imul    eax, ebx, 10

IN

Input from port

operands bytes 8088 186 286 386 486 Pentium
al, imm8 2 14 10 5 12 14 7 NP
ax, imm8 2 14 10 5 12 14 7 NP
eax, imm8 2 - - - 12 14 7 NP
al, dx 1 12 8 5 13 14 7 NP
ax, dx 1 12 8 5 13 14 7 NP
eax, dx 1 - - - 13 14 7 NP

Protected mode

operands bytes 386 486 Pentium
acc, imm 2 6/26/26 9/29/27 4/21/19 NP
acc, dx 1 7/27/27 8/28/27 4/21/19 NP

cycles for: CPL ⇐ IOPL / CPL > IOPL / V86

Example: 

         in      al, dx

INC

Increment

operand bytes 8088 186 286 386 486 Pentium
r8 2 3 3 2 2 1 1 UV
r16 1 3 3 2 2 1 1 UV
r32 1 3 3 2 2 1 1 UV
mem 2+d(0,2) 23+EA 15 7 6 3 3 UV

Example: 

        inc     ebx

INS/INSB/INSW/INSD

Input from port to string

variations bytes 8088 186 286 386 486 Pentium
insb 1 - 14 5 15 17 9 NP
insw 1 - 14 5 15 17 9 NP
insd 1 - - - 15 17 9 NP

Protected Mode

operand bytes 8088 186 286 386 486 Pentium
- 1 - - - 9/29/29 10/32/30 6/24/22 NP

cycles for: CPL ⇐ IOPL / CPL > IOPL / V86

Example: 

        rep insb

INT

Call interrupt procedure

operands bytes 8088 186 286 386 486 Pentium
3 1 72 45 23+m 33 26 13 NP
imm8 2 71 47 23+m 37 30 16 NP

Protected mode

operands bytes 8088 186 286 386 486 Pentium
- 1 - - (40-78)+m 59-99 44-71 27-82 NP

Example: 

        int     21h

INTO

Call interrupt procedure if overflow

operand bytes 8088 186 286 386 486 Pentium
- 1 4/73 4/48 3/24+m 3/35 3/28 4/13 NP

Protected mode

operand bytes 8088 186 286 386 486 Pentium
- 1 - - (40-78)+m 59-99 44-71 27-56 NP

Task switch clocks not shown

Example: 

        into

INVD

Invalidate data cache (486+)

operand bytes 8088 186 286 386 486 Pentium
- 2 - - - - 4 15 NP

Example: 

        invd

INVLPG

Invalidate TLB entry (486+)

operand bytes 8088 186 286 386 486 Pentium
mem32 5 - - - - 12 25 NP

Example: 

        invlpg  [eax]

IRET

Return from interrupt

operand bytes 8088 186 286 386 486 Pentium
- 1 44 28 17+m 22 15 8-27 NP

Task switch clocks not shown

Example: 

        iret

IRETD

32-bit return from interrupt (386+)

operand bytes 8088 186 286 386 486 Pentium
- 1 - - - 22 15 10-27 NP

Task switch clocks not shown

Example: 

        iretd

Jcc

Jump on condition code

operand bytes 8088 186 286 386 486 Pentium
near8 2 4 / 16 4 / 13 3 / 7+m 3 / 7+m 1 / 3 1 PV
near16 3 - - - 3 / 7+m 1 / 3 1 PV

cycles for: no jump/jump

conditional jump instructions:

ja jump if above jnbe jump if not below or equal
jae jump if above or equal jnb jump if not below
jb jump if below jnae jump if not above or equal
jbe jump if below or equal jna jump if not above
jg jump if greater jnle jump if not less or equal
jge jump if greater or equal jnl jump if not less
jl jump if less jnge jump if not greater or equal
jle jump if less or equal jng jump if not greater
je jump if equal jz jump if zero
jne jump if not equal jnz jump if not zero
jc jump if carry jnc jump if not carry
js jump if sign jns jump if not sign
jnp jump if no parity (odd) jpo jump if parity odd
jo jump if overflow jno jump if not overflow
jp jump if parity (even) jpe jump if parity even

Example: 

jne     not_equal

JCXZ/JECXZ

Jump if CX/ECX = 0

operand bytes 8088 186 286 386 486 Pentium
dest 2 6 / 18 5 / 16 4 / 8+m 5 / 9+m 5 / 8 5 / 6 NP
dest 2 - - - 5 / 9+m 5 / 8 5 / 6 NP

cycles for: no jump/jump

Example: 

        jcxz    cx_is_zero

JMP

Unconditional jump

operand bytes 8088 186 286 386 486 Pentium
short 2 15 13 7+m 7+m 3 1 PV
near 3 15 13 7+m 7+m 3 1 PV
far 5 15 13 11+m 12+m 17 3 NP
r16 2 11 11 7+m 7+m 5 2 NP
mem16 2+d(0,2) 18+EA 17 11+m 10+m 5 2 NP
mem32 2+d(4) 24+EA 26 15+m 12+m 13 4 NP
r32 2 - - - 7+m 5 2 NP
mem32 2+d(0,2) - - - 10+m 5 2 NP
mem48 2+d(6) - - - 12+m 13 4 NP

cycles for jumps through call gates not shown

Example: 

        jmp     target_address

LAHF

Load flags into AH

operand bytes 8088 186 286 386 486 Pentium
- 1 4 2 2 2 3 2 NP

Example: 

        lahf

LAR [UPDATE]

Load access rights byte (286+) 

  operands    bytes                   286     386     486     Pentium
  r16, r16     3                      14      15      11       8   NP
  r32, r32     3                       -      15      11       8   NP
  r16, m16     3                      16      16      11       8   NP
  r32, m32     3                       -      16      11       8   NP

Example: 

        lar     eax, ebx

LDS

Load far pointer 

  operands    bytes   8088    186     286     386     486     Pentium
  reg, mem   2+d(2)   24+EA   18       7       7       6       4   NP

Example: 

        lds     si, ptr_1

LES

Load far pointer 

  operands    bytes   8088    186     286     386     486     Pentium
  reg, mem   2+d(2)   24+EA   18       7       7       6       4   NP

Example: 

        les     di, ptr_2

LFS

Load far pointer (386+) 

  operands    bytes                           386     486     Pentium
  reg, mem   3+d(2,4)                          7       6       4   NP

Example: 

        lfs     si, ptr_3

LGS

Load far pointer (386+) 

  operands    bytes                           386     486     Pentium
  reg, mem   3+d(2,4)                          7       6       4   NP

Example: 

        lgs     si, ptr_4

LSS

Load stack segment and offset 

  operands    bytes                           386     486     Pentium
  reg, mem   3+d(2,4)                          7       6       4   NP

Example: 

        lss     bp, ptr_5

LEA

Load effective address 

  operands    bytes   8088    186     286     386     486     Pentium
  r16, mem    2+d(2)  2+EA     6       3       2      1-2      1   UV
  r32, mem    2+d(2)   -       -       -       2      1-2      1   UV

Example: 

        lea     eax, [eax+ebx*2+3]

LEAVE

High level procedure exit (186+) 

              bytes           186     286     386     486     Pentium
               1               8       5       4       5       3   NP

Example: 

        leave

LGDT

Load global descriptor table register (286+) 

  operand     bytes                   286     386     486     Pentium
   mem48       5                      11      11      11       6   NP

Example: 

        lgdt    descriptor[ebx]

LIDT

Load interrupt descriptor table register (286+) 

  operand     bytes                   286     386     486     Pentium
   mem48       5                      12      11      11       6   NP

Example: 

        lidt    descriptor[ebx]

LLDT

Load local descriptor table register (286+) 

  operand     bytes                   286     386     486     Pentium
   r16         3                      17      20      11       9   NP
   mem16     3+d(0-2)                 19      24      11       9   NP

Example: 

        lldt    ax

LMSW

Load machine status word (286+) 

  operand     bytes                   286     386     486     Pentium
   r16         3                       3      10      13       8   NP
   mem16     3+d(0-2)                  6      13      13       8   NP

Example: 

        lmsw    ax

LOCK

Lock bus on next instruction (prefix) 

              bytes   8088    186     286     386     486     Pentium
               1       2       2       0       0       1       1   NP
(Note: xchg always is locked whether it is specified or not)

Example: 

        lock    mov     mem, 1

LODS/LODSB/LODSW/LODSD

Load string operand 

  variations  bytes   8088    186     286     386     486     Pentium
  lodsb        1      16      10       5       5       5       2   NP
  lodsw        1      16      10       5       5       5       2   NP
  lodsd        1       -       -       -       5       5       2   NP

Example: 

        lodsb

LOOP

Loop control with CX counter 

    operand   bytes   8088    186     286     386     486     Pentium
    short      2      5/17    5/15    4/8+m   11+m    6/7     5/6  NP

loopw short (uses CX in 32-bit mode) loopd short (uses ECX in 16-bit mode)

Example: 

        loop    loop_start

LOOPE/LOOPZ

Loop while equal (or zero) 

    operand   bytes   8088    186     286     386     486     Pentium
    short      2      6/18    5/16    4/8     11+m    6/9     7/8  NP

loopew short (uses CX in 32-bit mode) loopzw short (uses CX in 32-bit mode) looped short (uses ECX in 16-bit mode) loopzd short (uses ECX in 16-bit mode)

Example: 

        loope   loop_start

LOOPNE/LOOPNZ

Loop while not equal (or not zero) 

      operand bytes   8088    186     286     386     486     Pentium
      short    2      5/19    5/16    4/8     11+m    6/9     7/8  NP

loopnew short (uses CX in 32-bit mode) loopnzw short (uses CX in 32-bit mode) loopned short (uses ECX in 16-bit mode) loopnzd short (uses ECX in 16-bit mode)

Example: 

        loopne  loop_start

LSL

Load segment limit (286+) 

  operands    bytes                   286     386     486     Pentium
  r16, r16     3                      14      20/25   10       8   NP
  r32, r32     3                       -      20/25   10       8
  r16, m16   3+d(0,2)                 16      21/26   10       8
  r32, m32   3+d(0,2)                  -      21/26   10       8

Example: 

        lsl     eax, ebx

LTR

Load task register (286+) 

  operand     bytes                   286     386     486     Pentium
  r16          3                      17      23      20      10   NP
  mem16      3+d(0,2)                 19      27      20      10

Example: 

        ltr     ax

MOV

Move data

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 2 2 2 2 1 1 UV
mem, reg 2+d(0-2) 13+EA 9 3 2 1 1 UV
reg, mem 2+d(0-2) 12+EA 12 5 4 1 1 UV
mem, imm 2+d(0-2)
+i(1,2) 		14+EA 12-13 3 2 1 1 UV*
reg, imm 2+i(1,2) 4 3-4 2 2 1 1 UV
acc, mem 3 14 8 5 4 1 1 UV
mem, acc 3 14 9 3 2 1 1 UV

* : not pairable if there is a displacement and immediate

Example: 

    mov     eax, ebx

Segment Register Moves

Real Mode

operands bytes 8088 186 286 386 486 Pentium
seg, r16 2 2 2 2 2 3 2-11 NP
seg, m16 2+d(0,2) 12+EA 9 5 5 3 3-12 NP
r16, seg 2 2 2 2 2 3 1 NP
m16, seg 2+d(0,2) 13+EA 11 3 2 3 1 NP

Example: 

mov     ds, ax

Protected Mode Differences

operands bytes 286 386 486 Pentium
seg, r16 2 17 18 9 2-11* NP
seg, m16 2+d(0,2) 19 19 9 3-12* NP

MOVE to/from special registers (386+)

operands bytes 386 486 Pentium
r32, cr32 3 6 4 4 NP
cr32, r32 3 4/10* 4/16* 12/22* NP
r32, dr32 3 14/22* 10 2/12* NP
dr32, r32 3 16/22* 11 11/12* NP
r32, tr32 3 12 3/4* - NP
tr32, r32 3 12 4/6* - NP

* : cycles depend on which special register

Example: 

        mov     cr0, eax

MOVS/MOVSB/MOVSW/MOVSD

Move data from string to string 

  variations  bytes   8088    186     286     386     486     Pentium
  movsb        1      18       9       5       7       7       4   NP
  movsw        1      26       9       5       7       7       4   NP
  movsd        1       -       -       -       7       7       4   NP
  rep movsb    2      9+17n   8+8n    5+4n    7+4n   12+3n*   3+n  NP
  rep movsw    2      9+25n   8+8n    5+4n    7+4n   12+3n*   3+n  NP
  rep movsd    2       -       -       -      7+4n   12+3n*   3+n  NP
  • = 5 if n=0, 13 if n=1

(n = count of bytes, words or dwords)

Example: 

        rep movsb

MOVSX

Move with sign-extend (386+) 

    operands  bytes                           386     486     Pentium
    reg, reg   3                               3       3       3   NP
    reg, mem   3+d(0,1,2,4)                    6       3       3   NP
      (Note: destination reg is 16 or 32-bits; source is 8 or 16 bits)

Example: 

        movsx   ebx, ax

MOVZX

Move with zero-extend (386+) 

    operands  bytes                           386     486     Pentium
    reg, reg   3                               3       3       3   NP
    reg, mem   3+d(0,1,2,4)                    6       3       3   NP
      (Note: destination reg is 16 or 32-bits; source is 8 or 16 bits)

Example: 

        movzx   ebx, ax

MUL

Unsigned multiply 

  operand     bytes   8088     186    286     386     486     Pentium
  r8           2     70-77    26-28   13      9-14   13-18    11   NP
  r16          2    118-133   35-37   21      9-22   13-26    11   NP
  r32          2       -        -      -      9-38   13-42    10   NP
  mem8    2+d(0-2)  76-83+EA  32-34   16     12-17   13-18    11   NP
  mem16   2+d(0-2) 124-139+EA 41-43   24     12-25   13-26    11   NP
  mem32   2+d(0-2)     -        -      -     12-41   13-42    10   NP
   implied      operand      result
 multiplicand (multiplier)
      AL    *  byte       =  AX
      AX    *  word       =  DX:AX
      EAX   *  dword      =  EDX:EAX

Example: 

        mul     ebx

NEG

Two's complement negation 

  operand     bytes   8088    186     286     386     486     Pentium
  reg          2       3       3       2       2       1       1   NP
  mem       2+d(0-2)  24+EA   13       7       6       3       3   NP

Example: 

        neg     eax

NOP

No operation 

              bytes   8088    186     286     386     486     Pentium
               1       3       3       3       3       1       1   UV

Example: 

        nop

NOT

One's complement negation 

  operands    bytes   8088    186     286     386     486     Pentium
  reg          2       3       3       2       2       1       1   NP
  mem       2+d(0-2)  24+EA   13       7       6       3       3   NP

Example: 

        not     eax

OR

Logical inclusive or 

 operands     bytes   8088    186     286     386     486     Pentium
 reg, reg      2       3       3       2       2       1       1   UV
 mem, reg   2+d(0,2)  24+EA   10       7       7       3       3   UV
 reg, mem   2+d(0,2)  13+EA   10       7       6       2       2   UV
 reg, imm   2+i(1,2)   4       4       3       2       1       1   UV
 mem, imm   2+d(0,2)  23+EA   16       7       7       3       3   UV*
             +i(1,2)
 acc, imm   1+i(1,2)   4       4       3       2       1       1   UV
  • = not pairable if there is a displacement and immediate

Example: 

        or      eax, ebx

OUT

Output to port

operands bytes 8088 186 286 386 486 Pentium
imm8, al 2 14 9 3 10 16 12 NP
imm8, ax 2 14 9 3 10 16 12 NP
imm8, eax 2 - - - 10 16 12 NP
dx, al 1 12 7 3 11 16 12 NP
dx, ax 1 12 7 3 11 16 12 NP
dx, eax 1 - - - 11 16 12 NP

Protected Mode

operands bytes 386 486 Pentium
imm8, acc 2 4/24/24 11/31/29 9/26/24 NP
dx, acc 1 5/25/25 10/30/29 9/26/24 NP

cycles for: CPL ⇐ IOPL / CPL > IOPL / V86

Example: 

out     dx, al

OUTS/OUTSB/OUTSW/OUTSD

Output string to port 

  variations  bytes           186     286     386     486     Pentium
  outsb        1              14       5      14      17      13   NP
  outsw        1              14       5      14      17      13   NP
  outsd        1               -       -      14      17      13   NP

Protected mode 

              bytes                           386     486     Pentium
               1                           8/28/28 10/32/30 10/27/25 NP
             cycles for: CPL <= IOPL / CPL > IOPL / V86

Example: 

        rep outsw

POP

Pop a word/dword from the stack 

  operand     bytes   8088    186     286     386     486     Pentium
  reg          1      12      10       5       4       1       1   UV
  mem       2+d(0-2)  25+EA   20       5       5       6       3   NP
  seg          1      12       8       5       7       3       3   NP
  FS/GS        2       -       -       -       7       3       3   NP

Protected mode 

  operand     bytes                   286     386     486     Pentium
  CS/DS/ES     1                      20      21       9     3-12  NP
  SS           1                      20      21       9     8-17  NP
  FS/GS        2                       -      21       9     3-12  NP

Example: 

        pop     eax

POPA/POPAD

Pop all (186+)/Pop all double (386+) 

  variations  bytes           186     286     386     486     Pentium
  popa         1              51      19      24       9       5   NP
  popad        1               -       -      24       9       5   NP
popa  = pop di, si, bp, sp, bx, dx, cx, ax
popad = pop edi, esi, ebp, esp, ebx, edx, ecx, eax
        (sp and esp are discarded)

Example: 

        popa

POPF/POPFD

Pop flags/Pop flags double (386+) 

  variations  bytes   8088    186     286     386     486     Pentium
  popf         1      12       8       5       5       9       6   NP
  popfd        1       -       -       -       5       9       6   NP

Protected mode 

              bytes                   286     386     486     Pentium
  popf         1                       5       5       6       4   NP
  popfd        1                       -       5       6       4   NP

Example: 

        popf

PUSH

push a word/dword to the stack 

   operand    bytes   8088    186     286     386     486     Pentium
   reg         1      15      10       3       2       1       1   UV
   mem      2+d(0-2)  24+EA   16       5       5       4       2   NP
   seg         1      14       9       3       2       3       1   NP
   imm     1+i(1,2)    -       -       3       2       1       1   NP
   FS/GS       2       -       -       -       2       3       1   NP

Example: 

        push    eax

PUSHA/PUSHAD

Push all (186+)/Push all double (386+) 

  variations  bytes           186     286     386     486     Pentium
  pusha        1              36      17      18      11       5   NP
  pushad       1               -       -      18      11       5   NP
pusha  = push ax, cx, dx, bx, sp, bp, si, di,
pushad = push eax, ecx, edx, ebx, esp, ebp, esi, edi

Example: 

        pusha

PUSHF/PUSHFD

Push flags/Push flags double (386+) 

  variations  bytes   8088    186     286     386     486     Pentium
  pushf        1      14       9       3       4       4       9   NP
  pushfd       1       -       -       -       4       4       9   NP

Protected mode 

              bytes                   286     386     486     Pentium
  pushf        1                       3       4       3       3   NP
  pushfd       1                       -       4       3       3   NP

Example: 

        pushf

RCL

Rotate bits left with CF 

  operands    bytes   8088    186     286     386     486     Pentium
  reg, 1       2       2       2       2       9       3       1   PU
  mem, 1    2+d(0,2)  23+EA   15       7      10       4       3   PU
  reg, cl      2       8+4n    5+n    5+n      9      8-30    7-24 NP
  mem, cl   2+d(0,2) 28+EA+4n 17+n    8+n     10      9-31    9-26 NP
  reg, imm     3       -       5+n    5+n      9      8-30    8-25 NP
  mem, imm  3+d(0,2)   -      17+n    8+n     10      9-31   10-27 NP

Example: 

        rcl     eax, 16

RCR

Rotate bits right with CF 

  operands    bytes   8088    186     286     386     486     Pentium
  reg, 1       2       2       2       2       9       3       1   PU
  mem, 1    2+d(0,2)  23+EA   15       7      10       4       3   PU
  reg, cl      2       8+4n    5+n    5+n      9      8-30    7-24 NP
  mem, cl   2+d(0,2) 28+EA+4n 17+n    8+n     10      9-31    9-26 NP
  reg, imm     3       -       5+n    5+n      9      8-30    8-25 NP
  mem, imm  3+d(0,2)   -      17+n    8+n     10      9-31   10-27 NP

Example: 

        rcr     eax, 16

ROL

Rotate bits left 

  operands    bytes   8088    186     286     386     486     Pentium
  reg, 1       2       2       2       2       3       3       1   PU
  mem, 1    2+d(0,2)  23+EA   15       7       7       4       3   PU
  reg, cl      2       8+4n    5+n    5+n      3       3       4   NP
  mem, cl   2+d(0,2) 28+EA+4n 17+n    8+n      7       4       4   NP
  reg, imm     3       -       5+n    5+n      3       2       1   PU
  mem, imm  3+d(0,2)   -      17+n    8+n      7       4       3   PU*
  • = not pairable if there is a displacement and immediate

Example: 

        rol     eax, 16

ROR

Rotate bits right 

  operands    bytes   8088    186     286     386     486     Pentium
  reg, 1       2       2       2       2       3       3       1   PU
  mem, 1    2+d(0,2)  23+EA   15       7       7       4       3   PU
  reg, cl      2       8+4n    5+n    5+n      3       3       4   NP
  mem, cl   2+d(0,2) 28+EA+4n 17+n    8+n      7       4       4   NP
  reg, imm     3       -       5+n    5+n      3       2       1   PU
  mem, imm  3+d(0,2)   -      17+n    8+n      7       4       3   PU*
  • = not pairable if there is a displacement and immediate

Example: 

        ror     eax, 16

RDMSR

Read from model specific register (Pentium+) 

              bytes                                           Pentium
              2                                              20-24 NP

Example: 

        rdmsr

REP

Repeat string operation 

See:  MOVS (rep movs)         move block
See:  STOS (rep stos)         fill block

REPE

Repeat while equal (or zero) string operation 

See:  CMPS (repe cmps)        find non-matching memory items
See:  CMPS (repe scas)        find non-acc matching byte in memory

REPNE

Repeat while not equal (or not zero) string operation 

See:  CMPS (repne cmps)       find first matching memory items
See:  SCAS (repne scas)       find first matching memory item to acc

RET/RETN/RETF

Return from procedure 

 variations/
 operands     bytes   8088    186     286     386     486     Pentium
 retn         1       20      16      11+m    10+m     5       2   NP
 retn imm16   1+d(2)  24      18      11+m    10+m     5       3   NP
 retf         1       34      22      15+m    18+m    13       4   NP
 retf imm16   1+d(2)  33      25      15+m    18+m    14       4   NP

RET is coded by the assembler as near or far based on the procedure declaration and program model, as: 

      RETN (return near)
      RETF (return far)

Example: 

        ret

Protected mode 

  variations/
  operands    bytes                   286     386     486     Pentium
  retf        1                     25+m/55  32+m/62 18/33  4-13/23 NP
  retf imm16  1+d(2)                25+m/55  32+m/68 17/33  4-13/23 NP

cycles for: same privilege level/lower privilege level

RSM

Resume from system management mode (Pentium+) 

              bytes                                           Pentium
               2                                              83   NP

Example: 

        rsm

SAL/SHL/SAR/SHR

Shift bits 

 operands     bytes   8088    186     286     386     486     Pentium
 reg, 1        2       2       2       2       3       3       1   PU
 mem, 1     2+d(0,2)  23+EA   15       7       7       4       3   PU
 reg, cl       2       8+4n    5+n    5+n      3       3       4   NP
 mem, cl    2+d(0,2) 28+EA+4n 17+n    8+n      7       4       4   NP
 reg, imm      3       -       5+n    5+n      3       2       1   PU
 mem, imm   3+d(0,2)   -      17+n    8+n      7       4       3   PU*
  • = not pairable if there is a displacement and immediate
 sal = shift arithmetic left         sar =  shift arithmetic right
 shl = shift left (same as sal)      shr =  shift right

Example: 

        shl     eax, 1

SAHF

Store AH into flags 

              bytes   8088    186     286     386     486     Pentium
               1       4       3       2       3       2       2   NP

Example: 

        sahf

SBB

Integer subtraction with borrow 

  operands    bytes   8088    186     286     386     486     Pentium
  reg, reg     2       3       3       2       2       1       1   PU
  mem, reg  2+d(0,2)  24+EA   10       7       7       3       3   PU
  reg, mem  2+d(0,2)  13+EA   10       7       6       2       2   PU
  reg, imm  2+i(1,2)   4       4       3       2       1       1   PU
  mem, imm  2+d(0,2)  23+EA   16       7       7       3       3   PU*
             +i(1,2)
  acc, imm  1+i(1,2)   4       4       3       2       1       1   PU
  • = not pairable if there is a displacement and immediate

Example: 

        sbb     eax, ebx

SCAS/SCASB/SCASW/SCASD

Scan string data 

  variations  bytes   8088    186     286     386     486     Pentium
  scasb        1      19      15       7       7       6       4   NP
  scasw        1      19      15       7       7       6       4   NP
  scasd        1       -       -       -       7       6       4   NP
  repX scasb   2      9+15n   5+15n   5+8n    5+8n    7+5n*   8+4n NP
  repX scasw   2      9+19n   5+15n   5+8n    5+8n    7+5n*   8+4n NP
  repX scasd   2       -       -       -      5+8n    7+5n*   8+4n NP
  repX = repe or repz or repne or repnz
  • = 5 if n=0

(n = count of bytes, words or dwords)

Example: 

        repne   scasb

SET

Set byte to 1 on condition else set to 0 (386+) 

    operand   bytes                           386     486     Pentium
    r8         3                               4      4/3     1/2  NP
    mem8     3+d(0-2)                          5      3/4     1/2  NP
                      Cycles are for:  true/false
setCC = one of:
   seta    setae   setb    setbe   setc    sete
   setg    setge   setl    setle   setna   setnae
   setnb   setnbe  setnc   setne   setng   setnge
   setnl   setnle  setno   setnp   setns   setnz
   seto    setp    setpe   setpo   sets    setz

Example: 

        setne   al

SGDT

Store global descriptor table register (286+) 

   operand    bytes                   286     386     486     Pentium
   mem48       5                      11       9      10       4   NP

Example: 

        sgdt    descriptor[ebx]

SIDT

Store interrupt descriptor table register (286+) 

   operand    bytes                   286     386     486     Pentium
   mem48       5                      12       9      10       4   NP

Example: 

        sidt    descriptor[ebx]

SHLD

Double precision shift left (386+) 

   operands        bytes                      386     486     Pentium
   reg, reg, imm    4                          3       2       4   NP
   mem, reg, imm   4+d(0-2)                    7       3       4   NP
   reg, reg, cl     4                          3       3       4   NP
   mem, reg, cl    4+d(0-2)                    7       4       5   NP

Example: 

        shld    eax, ebx, 16

SHRD

Double precision shift right (386+) 

   operands        bytes                      386     486     Pentium
   reg, reg, imm    4                          3       2       4   NP
   mem, reg, imm   4+d(0-2)                    7       3       4   NP
   reg, reg, cl     4                          3       3       4   NP
   mem, reg, cl    4+d(0-2)                    7       4       5   NP

Example: 

        shrd    eax, ebx, 16

SLDT

Store local descriptor table register (286+) 

   operands   bytes                   286     386     486     Pentium
   r16         3                       2       2       2       2   NP
   mem16     3+d(0-2)                  3       2       3       2   NP

Example: 

        sldt    ax

SMSW

Store machine status word (286+) 

   operands   bytes                   286     386     486     Pentium
   r16         3                       2       2       2       4   NP
   mem16     3+d(0-2)                  3       3       3       4   NP

Example: 

        smsw    ax

STC

Set the carry flag 

              bytes   8088    186     286     386     486     Pentium
               1       2       2       2       2       2       2   NP

Example: 

        stc

STD

Set direction flag (set to reverse string direction) 

              bytes   8088    186     286     386     486     Pentium
               1       2       2       2       2       2       2   NP

Example: 

        std

STI

Set interrupt flag (enable) 

              bytes   8088    186     286     386     486     Pentium
               1       2       2       2       3       5       7   NP

Example: 

        sti

STOS/STOSB/STOSW/STOSD

Store string data

variations bytes 8088 186 286 386 486 Pentium
stosb 1 11 10 3 4 5 3 NP
stosw 1 15 10 3 4 5 3 NP
stosd 1 - - - 4 5 3 NP
rep stosb 2 9+10n 6+9n 4+3n 5+5n 7+4n* 3+n NP
rep stosw 2 9+14n 6+9n 4+3n 5+5n 7+4n* 3+n NP
rep stosd 2 - - - 5+5n 7+4n* 3+n NP

* = 5 if n=0, 13 if n=1

(n = count of bytes, words or dwords)

Example: 

        rep     stosd

STR

Store task register (286+)

operand bytes 286 386 486 Pentium
r16 3 2 2 2 2 NP
mem16 3+d(0-2) 3 2 3 2 NP

Example: 

        str     bx

SUB

Integer subtraction

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 3 3 2 2 1 1 UV
mem, reg 2+d(0,2) 24+EA 10 7 7 3 3 UV
reg, mem 2+d(0,2) 13+EA 10 7 6 2 2 UV
reg, imm 2+i(1,2) 4 4 3 2 1 1 UV
mem, imm 2+d(0,2)
+i(1,2) 		23+EA 16 7 7 3 3 UV*
acc, imm 1+i(1,2) 4 4 3 2 1 1 UV

* : not pairable if there is a displacement and immediate

Example: 

        sub     eax, ebx

TEST

Logical compare

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 3 3 2 2 1 1 UV
mem, reg 2+d(0,2) 13+EA 10 6 5 2 2 UV
reg, mem 2+d(0,2) 13+EA 10 6 5 2 2 UV
reg, imm 2+i(1,2) 5 4 3 2 1 1 UV
mem, imm 2+d(0,2)
+i(1,2) 		11+EA 10 6 5 2 2 UV*
acc, imm 1+i(1,2) 4 4 3 2 1 1 UV

* : not pairable if there is a displacement and immediate

Example: 

       sub     eax, ebx

VERR

Verify a segment for reading (286+)

operands bytes 8088 186 286 386 486 Pentium
r16 3 - - 14 10 11 7 NP
mem16 3+d(0,2) - - 16 11 11 7 NP

Example: 

        verr    ax

VERW

Verify a segment for writing (286+)

operands bytes 8088 186 286 386 486 Pentium
r16 3 - - 14 15 11 7 NP
mem16 3+d(0,2) - - 16 16 11 7 NP

Example: 

        verr    ax

WAIT

Wait for co-processor

operands bytes 8088 186 286 386 486 Pentium
- 1 4 6 3 6 1-3 1 NP

Example: 

        wait

WBINVD

Write-back and invalidate data cache (486+)

operands bytes 8088 186 286 386 486 Pentium
- 2 - - - - 5 2000+ NP

Example: 

        wbinvd

WRMSR

Write to model specific register (PENTIUM+)

operands bytes 8088 186 286 386 486 Pentium
- 2 - - - - - 30-45 NP

Example: 

        wrmsr

XADD

Exchange and add (486+)

operands bytes 8088 186 286 386 486 Pentium
reg, reg 3 - - - - 3 3 NP
mem, reg 3+d(0-2) - - - - 4 4 NP

Example: 

        xadd    eax, ebx

XCHG

Exchange register/memory with register

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 4 4 3 3 3 3 NP
reg, mem 2+d(0-2) 25+EA 17 5 5 5 3 NP
mem, reg 2+d(0-2) 25+EA 17 5 5 5 3 NP
acc, reg 1 3 3 3 3 3 2 NP
reg, acc 1 3 3 3 3 3 2 NP

in above: acc = AX or EAX only

Example: 

        xchg    ax, dx

XLAT/XLATB

Table look-up translation

operands bytes 8088 186 286 386 486 Pentium
- 1 11 11 5 5 4 4 NP

Example: 

        xlat

XOR

Logical exclusive or

operands bytes 8088 186 286 386 486 Pentium
reg, reg 2 3 3 2 2 1 1 UV
mem, reg 2+d(0,2) 24+EA 10 7 7 3 3 UV
reg, mem 2+d(0,2) 13+EA 10 7 6 2 2 UV
reg, imm 2+i(1,2) 4 4 3 2 1 1 UV
mem, imm 2+d(0,2)
+i(1,2) 		23+EA 16 7 7 3 3 UV*
acc, imm 1+i(1,2) 4 4 3 2 1 1 UV

* : not pairable if there is a displacement and immediate

Example: 

        xor     eax, ebx
back2root/archives/80x88.txt · Dernière modification : 2022/11/09 23:26 de frater

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