Intel Pentium CPU Instruction Set Reference
WAIT instruction - Wait
| Code |
Mnemonic |
Description |
| 9B |
WAIT |
Check pending unmasked floating-point exceptions. |
| 9B |
FWAIT |
Check pending unmasked floating-point exceptions. |
Description
Causes the processor to check for and handle pending, unmasked, floating-point exceptions before proceeding. (FWAIT is an alternate mnemonic for the WAIT).
This instruction is useful for synchronizing exceptions in critical sections of code. Coding a WAIT instruction after a floating-point instruction insures that any unmasked floating-point exceptions the instruction may raise are handled before the processor can modify the instruction's results. See the section titled "Floating-Point Exception Synchronization" in Chapter 7 of the Intel Architecture Software Developer's Manual, Volume 1, for more information on using the WAIT/FWAIT instruction.
| Operands |
Bytes |
Clocks |
|
1 |
1 |
NP |
Flags
| ID |
unaffected |
DF |
unaffected |
| VIP |
unaffected |
IF |
unaffected |
| VIF |
unaffected |
TF |
unaffected |
| AC |
unaffected |
SF |
unaffected |
| VM |
unaffected |
ZF |
unaffected |
| RF |
unaffected |
AF |
unaffected |
| NT |
unaffected |
PF |
unaffected |
| IOPL |
unaffected |
CF |
unaffected |
| OF |
unaffected |
