Every output bit m of microcode can be equivalently expressed as a logic function of n inputs where the microcode has n incoming address lines. This no less transparent than pure logic if you know the contents of the microcode. Microcode is often preferred because changing it is much easier than changing a bunch of gate logic. IMHO factoring your design into registers vs. control signals and putting the control signals into microcode makes the design more transparent than having a giant sea of gates.

https://en.wikipedia.org/wiki/Simple-As-Possible_computer

Back in the day i built a 4-bit CPU on a breadboard (it was huge actually spanned 3 breadboards). Programming the ROM by hand like cavemen (to be fair it was the cave ages). We didn’t carry cameras in our pockets so sadly we didn’t get a picture.

It doesn't appear to have any kind of interrupts, which is quite a limitation for actual usecases, but also makes the architecture much simpler.

The use of dual phase clocking is interesting. The document describes it as having the control and data paths operating on opposite phases. I'm curious as to where you got this technique from, since it's not common (apart from the use of both edges by DDR RAM). I also suspect that it would go away if you had better tooling for managing setup and hold violations (does logisim do that for you, or did you have to manage it manually somehow?). Not all FPGA tools like nonstandard clock architectures.

Very implressive tbh

You should include a screenshot of the logisim diagram

Now do it the other way round and make the 8 bit cpus become a 2nd year EE student.

My friends and I...