x86 Is an Octal Machine (1995)

Post by mananaysiempre » Wed, Mar 02, 2022, 11:37 AM UTC

kens wrote: post #12

klelatti wrote: post #3

Earlier quoted context omitted.

Thanks for these links - very interesting. Astonishing to think that we can see traces of the 8008 still today and that it wasn’t actually an Intel designed ISA (came from CTC / Datapoint).

The Datapoint 2200, the source of the 8008 instruction set, is an interesting machine. The CPU was built from TTL chips. To decode instructions, they used decimal BCD decoder chips, specifically the 7442. But they'd use them as octal decoder chips, only using 8 outputs. The Datapoint 2200 documentation gave the opcodes in octal, so they were clearly thinking in octal. The 8008 documentation, however, didn't use octal…