Intel Pentium CPU Instruction Set Reference
IDIV instruction - Signed Divide
| Code |
Mnemonic |
Description |
| F6 /7 |
IDIV r/m8 |
Signed divide AX (where AH must contain sign-extension of AL) by r/m byte. (Results: AL=Quotient, AH=Remainder) |
| F7 /7 |
IDIV r/m16 |
Signed divide DX:AX (where DX must contain sign-extension of AX) by r/m word. (Results: AX=Quotient, DX=Remainder) |
| F7 /7 |
IDIV r/m32 |
Signed divide EDX:EAX (where EDX must contain sign-extension of EAX) by r/m doubleword. (Results: EAX=Quotient, EDX=Remainder) |
Description
Divides (signed) the value in the AL, AX, or EAX register by the source operand and stores the result in the AX, DX:AX, or EDX:EAX registers. The source operand can be a general-purpose register or a memory location. The action of this instruction depends on the operand size, as shown in the following table:
| Operand Size |
Dividend |
Divisor |
Quotient |
Remainder |
Quotient Range |
| Word / Byte |
AX |
r/m8 |
AL |
AH |
-128 to +127 |
| Doubleword / Word |
DX:AX |
r/m16 |
AX |
DX |
-32,768 to +32,767 |
| Quadword / Doubleword |
EDX:EAX |
r/m32 |
EAX |
EDX |
-2,147,483,648 to 4,294,967,295 (-2^31 to 2^32 - 1) |
Non-integral results are truncated (chopped) towards 0. The sign of the remainder is always the same as the sign of the dividend. The absolute value of the remainder is always less than the absolute value of the divisor. Overflow is indicated with the #DE (divide error) exception rather than with the OF (overflow) flag.
| Operands |
Bytes |
Clocks |
| r8 |
2 |
22 |
NP |
| r16 |
2 |
30 |
NP |
| r32 |
2 |
46 |
NP |
| mem8 |
2 + d(0 - 2) |
22 |
NP |
| mem16 |
2 + d(0 - 2) |
30 |
NP |
| mem32 |
2 + d(0 - 2) |
46 |
NP |
Flags
| ID |
unaffected |
DF |
unaffected |
| VIP |
unaffected |
IF |
unaffected |
| VIF |
unaffected |
TF |
unaffected |
| AC |
unaffected |
SF |
undefined |
| VM |
unaffected |
ZF |
undefined |
| RF |
unaffected |
AF |
undefined |
| NT |
unaffected |
PF |
undefined |
| IOPL |
unaffected |
CF |
undefined |
| OF |
undefined |
