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FUCOMP    Unordered Compare and Pop (80387)        Exception Flags: I D S

FUCOMP [register]

       Logic:      sets condition codes in the status word as follows
                   and then pops the stack:

                   C3 C2 C1 C0    Means
                   -- -- -- --    -----------
                   0  0  ?  0     ST > source
                   0  0  ?  1     ST < source
                   1  0  ?  0     ST = source
                   1  1  ?  1     unordered

     FUCOMP compares two registers, leaves the result encoded in the
     status word as shown above, and pops the stack. If no source
     register is specified, ST(1) is compared to ST. Otherwise, the
     source register is compared to ST.

     FUCOMP is like FCOMP except that it does not cause an invalid
     operation exception if one of the operands is a NAN. Instead, it
     sets the condition codes to give an unordered result.

  --------------------------------------------------------------------------
   Operands            Clocks         Bytes           Example
   FUCOMP reg          26               3             FUCOMP ST(1)
  --------------------------------------------------------------------------

        Note:          Use JP to test for an unordered comparison.