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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.


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


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