Function:
FRSTPM tells the FPU to use the data format specified in the Real-Mode
format of the <FSTENV> and <FSAVE> instructions.
These instructions save different types of data depending on the current
operating mode of the FPU.
The instruction only has a meaning on the 287 and 287xl.
FSCALE Adds the integer number in ST(1) to the exponent of ST
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