FLDCW           Load control word                    Exceptions: None
                                                     C3 C2 C1 C0: ? ? ? ?
FLDCW source

        Logic   control word ← source

    FLDCW replaces the current value of the FPU control word register
    with the value contained in the specified memory word; it is used to
    change the FPU's mode of operation, e.g. rounding control.

    Note
    If an exception bit in the status word is set, loading a new control
    word will produce a floating-point error condition. To avoid this
    problem, any pending exceptions should be cleared (for example, by
    using FCLEX) before loading the new control word.


    Opcode      Format
    D9 /5       FLDCW m16


    Timing
    Operand       8087         287        387      486     Pentium
    m16          (7-14)+EA     7-14       19        4       7      NP