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


FPU Flags

The C0, C1, C2, and C3 flags are undefined.

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