5 ms·
I think the most probable reason for this instruction is for calculating parity bits. This would need to be done fast so it makes sense that there would be a CP
by markh1967 7y ago
I think the most probable reason for this instruction is for calculating parity bits. This would need to be done fast so it makes sense that there would be a CPU instruction to do most of the work.
- kps 7y agoParity is much easier than counting. It's so easy that you get it for free in the x86 flags register. (… and because the 8008 was designed to run a terminal.)
- bogomipz 7y ago>"(… and because the 8008 was designed to run a terminal.)" Could you elaborate on this? How does the 8008 being designed to run a terminal relate to the parity and the flags register?
- kps 7y agoEach iteration from the 8080 through x64 have a parity bit in the flags register for backwards compatibility with the previous generation. The 8008 was a microprocessor implementation of the Datapoint 2200 architecture.
- bogomipz 7y agoExcellent, thanks for the insights. Cheers.
- ryacko 7y agoEarly protocols didn’t have error correction in the lower layers. The parity flag was equivalent to a CRC instruction nowadays. Presumably if parity was incorrect, that would mean the byte was transmitted incorrectly.