HSC – Halt and Spontaneously Combust
According to the MIPS-X Instruction Set and Programmer's Manual (PDF), it looks like you might need to be very careful if you're programming the MIPS-X. There's apparently an opcode whose mnemonic is HSC, for "Halt and Spontaneously Combust." Here's how this manual describes this instruction:
The processor stops fetching instructions and self destructs.
Note that the contents of Reg(31) are actually lost.
This is executed by the processor when a protection violation is detected. It is a privileged instruction available only on the -NSA versions of the processor.
The MIPS-X processor was developed with DARPA funding back in roughly 1984 to 1986 and never actually made it into any commercial designs, at least none that I've ever heard of. Maybe the existence of the HSC instruction wasn't responsible for this, but I'd certainly be wary of using it in anything.
"It doesn't actually spontaneously combust," the government program manager tells you. "And even if it did, that capability wouldn't be in the commercial versions. So there's absolutely no way that your equipment will ever explode for no obvious reason."
"OK. Maybe we'll just stick with the 8086 for now."