Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1688

WAIT/FWAIT—Wait
Opcode
9B
9B
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.
Operation
CheckPendingUnmaskedFloatingPointExceptions;
FPU Flags Affected
The C0, C1, C2, and C3 flags are undefined.
Floating-point Exceptions
None.
Protected Mode Exceptions
#NM
Real Address Mode Exceptions
#NM
Virtual 8086 Mode Exceptions
#NM
4:386
Instruction Description
WAIT Check pending unmasked floating-point exceptions.
FWAIT Check pending unmasked floating-point exceptions.
MP and TS in CR0 is set.
MP and TS in CR0 is set.
MP and TS in CR0 is set.
Volume 4: Base IA-32 Instruction Reference