WAIT
Usage: WAIT Modifies flags: None
FWAIT
CPU enters wait state until the coprocessor signals it has finished its operation. This instruction is used to prevent the CPU from accessing memory that may be temporarily in use by the coprocessor. WAIT and FWAIT are identical.
Wait for Floating-Point Processor
WAIT ; 9B [8086]
FWAIT ; 9B [8086]
WAIT, on 8086 systems with a separate 8087 FPU, waits for the FPU to have finished any operation it is engaged in before continuing main processor operations, so that (for example) an FPU store to main memory can be guaranteed to have completed before the CPU tries to read the result back out.
On higher processors, WAIT is unnecessary for this purpose, and it has the alternative purpose of ensuring that any pending unmasked FPU exceptions have happened before execution continues.
All the FPU Instructions that would actually require a WAIT are directely encoded with a 09B Prefix. These Instructions are FSAVE, FINIT, FCLEX, FSTCW, FSTSW, FSTENV.
EXAMPLE:
wait
fwait
WAIT
Usage: WAIT Modifies flags: None
FWAIT
CPU enters wait state until the coprocessor signals it has finished its operation. This instruction is used to prevent the CPU from accessing memory that may be temporarily in use by the coprocessor. WAIT and FWAIT are identical.
Wait for Floating-Point Processor
WAIT ; 9B [8086]
FWAIT ; 9B [8086]
WAIT, on 8086 systems with a separate 8087 FPU, waits for the FPU to have finished any operation it is engaged in before continuing main processor operations, so that (for example) an FPU store to main memory can be guaranteed to have completed before the CPU tries to read the result back out.
On higher processors, WAIT is unnecessary for this purpose, and it has the alternative purpose of ensuring that any pending unmasked FPU exceptions have happened before execution continues.
All the FPU Instructions that would actually require a WAIT are directely encoded with a 09B Prefix. These Instructions are FSAVE, FINIT, FCLEX, FSTCW, FSTSW, FSTENV.
EXAMPLE:
wait
fwait