Intel IA-32 - Manual (Page 205)

Vol. 3A 5-29
INTERRUPT AND EXCEPTION HANDLING
Interrupt 2—NMI Interrupt
Exception Class Not applicable.
Description
The nonmaskable interrupt (NMI) is generated externally by asserting the processor’s NMI pin
or through an NMI request set by the I/O APIC to the local APIC. This interrupt causes the NMI
interrupt handler to be called.
Exception Error Code
Not applicable.
Saved Instruction Pointer
The processor always takes an NMI interrupt on an instruction boundary. The saved contents of
CS and EIP registers point to the next instruction to be executed at the point the interrupt is
taken. See Section 5.5, “Exception Classifications,” for more information about when the
processor takes NMI interrupts.
Program State Change
The instruction executing when an NMI interrupt is received is completed before the NMI is
generated. A program or task can thus be restarted upon returning from an interrupt handler
without loss of continuity, provided the interrupt handler saves the state of the processor before
handling the interrupt and restores the processor’s state prior to a return.