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.