[cctalk] Re: System 360 question

The 6502 had a HCF (halt and catch fire) undocumented instruction. I forget the opcode and if you knew what you were doing you could get the instruction executed on the chip using any assembler. Security through obscurity back in the 70s. The chip was advanced enough that the DOD wanted to avoid it falling into the “wrong” hands. David Sent from iPhone Hotblack Desiato