NMI

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On MIPS there is an NMI but it's more intended as an exception for when things have gone catastrophically wrong. It jumps straight straight to the reset address in the firmware and most firmware implementations don't bother making the fine difference between NMI, soft reset and reset and will just reset the system. A few allow tapping it and on those systems the NMI is being used for debugging systems only. These systems include the MIPS Malta where there is an NMI pushbutton and the SGI IP27 and IP35 where the system controller can be used to send an NMI.

Caveat

NMI being unmaskable with interrupt any and all exception handler, including other exceptions using the ErrorEPC register. This makes an NMI that interrupts a Cache Error Exception non-recoverable. Then again the Cache Error' may have been non-recoverable anyway.