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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.
A Instructions
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
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