Function:

FENI Clears the interrupt enable mask in the FPU Control Word, effectively
allowing the FPU to generate interrupts. FNENI does not issue a WAIT
before doing this. These instruction only have a meaning on 87s.

FDISI Sets the interrupt enable mask in the FPU Control Word, effectively
denying the FPU to generate interrupts. FNDISI does not issue a WAIT
before doing this. These instruction only have a meaning on 87s.

All these instructions are effectively ignored on the 287+.
They do not cause an invalid opcode exception.




FPREM  Calculate modulus of ST by ST(1), store in ST
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