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Vol. 2A 3-265
INSTRUCTION SET REFERENCE, A-M
DIV—Unsigned Divide
Operation
IF SRC = 0
THEN #DE; FI; (* Divide Error *)
IF OperandSize = 8 (* Word/Byte Operation *)
THEN
temp ← AX / SRC;
IF temp > FFH
THEN #DE; (* Divide error *)
ELSE
AL ← temp;
AH ← AX MOD SRC;
FI;
ELSE IF OperandSize
= 16 (* Doubleword/word operation *)
THEN
temp ← DX:AX / SRC;
IF temp > FFFFH
THEN #DE; (* Divide error *)
ELSE
AX ← temp;
DX ← DX:AX MOD SRC;
FI;
FI;
ELSE IF Operandsize = 32 (* Quadword/doubleword operation *)
THEN
temp ← EDX:EAX / SRC;
IF temp > FFFFFFFFH
THEN #DE; (* Divide error *)
ELSE
EAX ← temp;
EDX ← EDX:EAX MOD SRC;
FI;
FI;
Table 3-20. DIV Action
Operand Size Dividend Divisor Quotient Remainder
Maximum
Quotient
Word/byte AX r/m8 AL AH 255
Doubleword/word DX:AX r/m16 AX DX 65,535
Quadword/doubleword EDX:EAX r/m32 EAX EDX 2
32
− 1
Doublequadword/
quadword
RDX:RAX r/m64 RAX RDX 2
64
− 1