FSTP              Store Real and Pop          Exception Flags: I O U P

FSTP destination

       Logic:      destination . ST
                   pop stack

     FSTP is the same as FST, except that it also pops the stack. It first
     stores the real value in ST into destination, which is either a long
     or short real memory location, or an ST(i) register. It then pops the
     stack. If the value in ST is longer than the memory location, it is
     rounded (according to the rounding control field, RC).

  --------------------------------------------------------------------------
   Operands            Clocks         Bytes           Example
   FSTP register       17-24            3             FSTP ST(1)
   FSTP MEMORY_REAL    52-106+EA        5             FSTP REAL_NUMBER
  --------------------------------------------------------------------------

        Note:          If ST is tagged as special (i.e. if it contains .,
                       a NAN, or a denormal), it is not rounded before
                       storage; the least significant bits are dropped.