Non-Maskable Interrupt

What Does Non-Maskable Interrupt Mean?

A non-maskable interrupt (NMI) is a type of hardware
interrupt (or signal to the processor) that prioritizes a certain thread
or process. Unlike other types of interrupts, the non-maskable interrupt cannot
be ignored through the use of interrupt masking techniques.

Techopedia Explains Non-Maskable Interrupt

Common examples of non-maskable interrupt include types of
internal system chipset errors, memory corruption problems, parity errors and
high-level errors needing immediate attention. In a sense, a non-maskable
interrupt is a way to prioritize certain signals within the operating system.
Another example is the user event non-maskable interrupt, where a user presses
control, alt, delete to create an immediate signal to the system when the
computer is not responding. This is a good example because it illustrates a
kind of “override” – rather than just following the general thread or process,
the ctrl-alt-delete produces a signal that the computer must and will deal with
immediately.