Comment by redox99
5 hours ago
> because Assembly doesn't have UB
To be pedantic, old hardware like 6502 family chips (Commodore 64, Apple II, etc) had illegal instructions which were often used by programmers, but it was completely up to the chip to do whatever it wanted with those like with UB.
> illegal instructions... were often used by programmers
Intentionally, with an expected effect? I'd need a citation for that.
Some desultory googling turned up:
* https://www.nesdev.org/wiki/CPU_unofficial_opcodes#Games_usi...
* https://hitmen.c02.at/files/docs/c64/NoMoreSecrets-NMOS6510U... (doesn't name any software, but some copy protection schemes were already known to use them)