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FNSTSW       Store Status Word (No-wait)      Exception Flags: None

FNSTSW memory location

       Logic:      [memory location] . status word

     FNSTSW is the no-wait form of FSTSW. It stores the current value of the
     status word to a 16-bit memory location. In the 80287 and 80387, you can
     store the status word directly to the AX register of the 80286 or 80386
     with the instruction FNSTSW AX.

     Use this instruction to poll the state of the coprocessor. You can use
     FNSTSW to determine if the coprocessor is busy.

  --------------------------------------------------------------------------
   Operands            Clocks         Bytes           Example
   FNSTSW memory16     12-18            4             FNSTSW STAT_WORD
  --------------------------------------------------------------------------

        Note:          You should use this no-wait form of the instruction
                       only when there is a danger of generating an infinite
                       wait condition.