Halt and Catch Fire
<humour, processor> (HCF) 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 Motorola 6800 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.