FENI            Enable interrupts                    Exceptions: None
FNENI           Enable interrupts, no wait           C3 C2 C1 C0: [??]

FENI
FNENI

        Logic   Interrupt Enable Mask ← 0

    FENI allows the 8087 only to generate interrupt requests by clearing
    the Interrupt Enable Mask in the control word. This instruction is
    recognized but ignored on later FPUs.

    FNENI is the no-wait form of FENI. It allows the 8087 only to
    generate interrupt requests by clearing the Interrupt Enable Mask in
    the control word. This instruction enables interrupts in the 8087
    only. It is recognized but ignored on later FPUs.


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


    Opcode      Format
    9B DB E0    FENI
    DB E0       FNENI


    Timing
    Variations    8087         287        387      486     Pentium
    feni          2-8           2          2        3       1      NP
    fneni         2-8           2          2        3       1      NP