I built a small 4-bit CPU that is really hard to program, because it heavily relies on swapping registers. It's basically a river-crossing puzzle. :)
If you want to try it out here's the Github link: https://github.com/gschwaer/Swappy/blob/main/Readme.md
you don't need that many registers all you need a is main memory and 2 accumulators for the processing, a 2nd larger main memory for Control unit and memory data registers, also known as MDR or multiple like Cache, Cache is THE main memory that is between the CPU and RAM what it dose is that it take HUGE chunks of memory at once (mostly 4 eight bit registers at once) then send it to the CPUs memory and control unit. it also sends data back to ram or to main bus. (about the memory input from ram to cache is much bigger than that IRL)
Thanks for your suggestions.
Why "that many registers"? I only have two. They are in the SWAPR4. (Btw, all the 4s refer to word size.)
I do not use a main memory, but two stacks (+1 for consts) and one code memory (in CMD4) instead. If you only have 4 bit as the instruction word, you don't want to waste a lot on immediates for offsets, nor with only 16 instructions on two word instructions. I don't understand what you wanted to imply regarding caches, surely in this simulator and on this level of CPU memory access latency plays not a role (compare with CPU in "the early days" like the 6502).
Yes, it's not a "classic" architecture, but I thing in might be Turing complete (assuming the stacks and program RAM would be infinite ;) ). I went for this arch because I wanted to test the individual chips well before putting them together (editing is not possible atm).
Merry Christmas! :)
