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This HTML version of the file intel.doc from the
PC Game Programmer's guide was produced by Zack T Smith. Fancy HTML modifications are copyright ©
2005 by Zack T Smith, all rights reserved.
This information is provided in the hope that it will be useful,
but without any warranty. It is provided AS-IS,
without even the implied warranty of fitness for a particular purpose.
C Instructions
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
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