Editing Non-maskable interrupt (section)

{{Short description|Hardware interrupt that cannot be ignored}}
In [[computing]], a '''non-maskable interrupt''' ('''NMI''') is a hardware [[interrupt]] that standard [[Interrupt#Masking|interrupt-masking techniques]] in the system cannot ignore. It typically occurs to signal attention for non-recoverable hardware [[error]]s. Some NMIs may be masked, but only by using proprietary methods specific to the particular NMI. With regard to [[SPARC]], the non-maskable interrupt (NMI), despite having the highest priority among interrupts, can be prevented from occurring through the use of an interrupt mask.<ref>{{cite web |url=https://docs.rtems.org/releases/rtems-4.11.2/cpu-supplement/sparc.html#interrupt-levels |title=Interrupt Levels |accessdate=2023-11-30}}</ref>

An NMI is often used when response time is critical or when an interrupt should never be disabled during normal system operation. Such uses include reporting non-recoverable hardware errors, system debugging and profiling, and handling of special cases like system resets.

Modern [[computer architecture]]s typically use NMIs to handle non-recoverable errors which need immediate attention. Therefore, such interrupts should not be masked in the normal operation of the system. These errors include non-recoverable internal system [[chipset]] errors, corruption in system memory such as [[parity bit|parity]] and [[Error correction code|ECC]] errors, and data corruption detected on system and peripheral buses.

On some systems, a computer user can trigger an NMI through hardware and software [[debugging]] interfaces and system reset buttons.

Programmers typically use debugging NMIs to diagnose and fix faulty code. In such cases, an NMI can execute an [[interrupt handler]] that transfers control to a special monitor program. From this program, a developer can inspect the machine's memory and examine the internal state of the program at the instant of its interruption. This also allows the debugging or diagnosing of computers which appear [[Hang (computing)|hung]].