4 ms·
Hmm, I don't know. Especially the way the segregate RAM into banks reminds me a lot of the x86 segments with their direct and indirect addressing modes. Also a
by noncoml 9y ago
Hmm, I don't know. Especially the way the segregate RAM into banks reminds me a lot of the x86 segments with their direct and indirect addressing modes.
Also a lot of instructions have similar names: CLC
You are right, it is not a true ancestor, but ready through the manual, it did seem to me that it was designed by the same people.
To be honest I haven't dig into other CPU families, so maybe these were pretty common.
But I can definitely see 4004 DNA in x86.
- anyfoo 9y agoThe 4004 is so weird that it stands in a class of its own, for me. I'm not sure how much of its instruction set came from Busicom, the company that the 4004 was made for, instead of from Intel engineers.
- kens 9y agoThe CLC - clear carry - instruction predates the 4004. The PDP-11 for instance used it. I think you're seeing patterns that aren't really there. One thing the 4004 and 8008 do have in common is a similar floor plan for the chips. They both have the ALU on the left, data bus along the top, instruction decoding in the middle, registers on the right, and on-chip stack on the right. Other processors of that era (e.g. 6800, 6502, 8080) have very different layouts so it's not just coincidence. Texas Instruments produced the TMC 1795, a chip equivalent to the 8008 (before the 8008), and it also has a completely different layout. If you look lower-level, at e.g. the ALU implementation or the register implementation or the pin drivers, there's less similarity. I would have expected they would essentially cut-and-paste some of these low-level pieces, but they are more different than I would expect.