Messages in this thread |  | | From | Kevin Lentin <> | Subject | Re: GLOAT BLOAT (Was: Boot messages, Ideas for v2.1) | Date | Tue, 25 Jun 1996 14:39:18 +1000 (EST) |
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Fred Love Wrote ... > > > > > Not a UNIX, but a CPU with a similar thing. One of the first versions > > of a CPU, I think it was the Z80, had a debugging instruction left in > > the instruction set that would toggle the voltage levels on one pin > > as fast as possible. This turned out to be let lethal to the electronics > > and so the instruction was named "Halt and catch fire". > > > > Can't even remember where I got this story from or if it's a urban legend > > of the computer bussines, so just take it for your personal amusement, > > > > Ralf > > No debug instructions in the Z80 instruction set, only one output > instruction was left undocumented by Mostek.
I should have replied to Ralf but I've lost the original mail. So I'll reply to Fred instead...
This is the HCF entry in the Jargon File:
:HCF: /H-C-F/ n. Mnemonic for `Halt and Catch Fire', any of several undocumented and semi-mythical machine instructions with destructive side-effects, supposedly included for test purposes on several well-known architectures going as far back as the IBM 360. The MC6800 microprocessor was the first for which an HCF opcode became widely known. This instruction caused the processor to {toggle} a subset of the bus lines as rapidly as it could; in some configurations this could actually cause lines to burn up.
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