OS & Hardware

Which describes an NMI (non-maskable interrupt)?

  1. AIt is accepted even when interrupts are masked and reports serious faults
  2. BIt has the lowest priority and is handled only after all other interrupts finish
  3. CIt is a timer-only interrupt that software can never trigger
Show answer and explanation

Answer: A. It is accepted even when interrupts are masked and reports serious faults

An NMI cannot be blocked by the usual interrupt-disable setting. It is used for events that must be reported even if the system is stuck, such as uncorrectable memory errors, power failures and watchdog timeouts. It can also be used to inspect state when the OS has hung with interrupts disabled. It is among the highest priorities, never deferred, and is not limited to timers.

  • A. Correct. It is accepted regardless of masking and reports serious faults.
  • B. NMIs are among the highest priorities and are never deferred.
  • C. It is not timer-only; it serves various critical events.
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