[sponaugle]

Correct! 74HCs for everything, which are both easy to get and forgiving to use. The first build has 4 PCBs ( ALU, Register file, instruction logic, and memory/LEDs/switches). Each PCB is 12-16 74HCx ICs.

I then did a second design of the same thing using Atmel 1504/1508 CPLDs, and that compressed the design to 2 PCBs - One for the CPU itself and a second for system ram, switches, LEDs, etc. That first board had 5 1504s and 1 1508, although it could have been done in a tad less if I used another 1508. The biggest consumer was the register file since it was 16x 8-bit register, which consumes 128 flip flops.

[kragen]

That sounds great! Have you written it up anywhere publicly? It sounds better designed (e.g., using less chips) than most of the SSI-board CPUs I've seen.

I've been thinking it would be fun to see if I could get JLCPCB to build me such a CPU out of SSI with their PCB assembly service. In theory this is nice and simple: I design the processor at the chip/netlist level, debug the thing in a discrete-event or synchronous simulation with Logisim or something, import it into KiCAD, produce some board layouts, send it to them along with US$50 or so, get back a stack of fully populated SMD PCBs, plug them together, plug it in, start single-stepping the clock while watching what's going on, and then ramp the clock up to see how fast it can run reliably. What surprises am I likely to run into?

Unfortunately I don't think Potato Chips' product line covers things like 1GHz 8-bit registers, but if so that would be pretty entertaining.