Finally, an update!

A project log for 4-bit CPU (TD4 once again)

I build TD4 CPU and expand it (add RAM, switchable memory banks and rugged I/O)

Fedor GruzdevFedor Gruzdev 10/18/2018 at 09:150 Comments

After almost 2 weeks since projects' creation it's time to write a log, isn't it? I've got a few things to post.

First, now there's a link to Github repo with some code written by my friend with whom we started this. As he is more about software than hardware, he writes "SDK" (if you can call it this).  For now, there are assembler/disassembler and emulator. This is enough to start writing programs (although you can do this using nothing but a sheet of paper but still).

Second, I finally assembed ROM PCB!

It's wired point-to-point using enameled wire. I saw this technique here on HaD (by the way, I hihgly reccomend visiting Elm's site,, there's a lot of great stuff over there (check out the pictures!)). That's a time-consuming process, but the results look very nice (do they?). I've also made it swappable, so it's possible to develop program using this PCB and than make a smaller hard-wired diode-only version (true firmware BTW).

Next thing to do is to start assembling the main board, and the first part will be, of course, the IC9 replacement, discrete-logic ful adder!