FWAIT           Wait                                 Exceptions: None
                                                     C3 C2 C1 C0: ? ? ? ?
FWAIT                                                (CPU instruction)

        Logic   80x86 wait

    FWAIT pauses the system until any currently executing FPU
    instruction completes. This is required because the FPU on the
    80486 SX and earlier CPU/FPU combinations can execute instructions
    in parallel with the CPU. Therefore, any FPU instruction which reads
    or writes memory could suffer from a data hazard if the main CPU
    accesses that same memory location before the FPU reads or writes
    that location.

    The FWAIT instruction lets you synchronize the operation of the FPU
    by waiting until the completion of the current FPU instruction. This
    resolves the data hazard by, effectively, inserting an explict
    "stall" into the execution stream.


    Note
    FWAIT is the same instruction as the 80x86 WAIT instruction.


    Opcode      Format
    9B          FWAIT


    Timing
    Operand       8087         287        387      486     Pentium
    -              4            3          6       1-3     1-3     NP