@kenshirriff

The CP/M 2.2 command processor for the 8080 checked the Digital Research copyright notice and executed a HLT instruction to lock up the machine if it had been tampered with (e.g. pirated copy of the OS).

The 8086 version of CP/M used the same machine translated code, but typical 8086/88 machines were interrupt driven, waking the machine again at the next keystroke and thus rendering the anti-piracy check toothless.