To get both blinkenlights for registers and tri-state for bus driving, use two ’574 chips in parallel rather than a ’377 behind a ’245. Tie the clock and input lines together on both. Tie the output enable low on the one driving the blinkenlights. This way the chip that the rest of the CPU depends on doesn’t have the extra work of driving any load and you only have one chip’s worth of propagation delays.

Hi Will, absolutely amazing this, I love the 'money shot' up front, there are days my desk and yours could be swapped without either of us realizing right away what happened.

The Rigol deserves a blog post of its own, I've got one too and the better I get in using it the more I'm amazed at what it can do.

I've run into the same 'all you can get is SMD' which is fine for when you're finished but a lot harder while you're still figuring things out. This is where 'proper engineers' can go straight to the finish line and I always struggle.

You also develop some kind of sixth sense for when something is misbehaving. If you haven't read it yet, 'The Soul of a New Machine' might be to your liking.

best of luck with your project!

Oh, and I did read all the way to the end.

You have to be a little mad to do this but exceptionally mad to do it on at least 8 independent breadboards using no less than 4 different styles of jumper wire!

Any time I see rounded corners on a PCB I know someone put love into that board. Well done

Of course while you're doing the next version you should knock out a tiny tapeout version, it should easily fit in a single cell (maybe 2 if you want to push the 256 byte sram in as well)

Hello Will, interesting read, and happy to see 8-bit breadboard builds on HN. I used to follow Ben and James years ago and built a fully functional 256-byte ROM/RAM cpu that could accept instructions from Arduino as a IO input. I gave up on extending output to add a mini OLED. Cool to see your project and can't wait for part 4.

Also tried to homebrew CPUs before but couldn't even start due to a wall of things to prepare;

Seeing this is just amazing to be honest. Wish you a luck on your project!

I always applaud homebrew cpu designs but after doing so many myself I would reaaaaly advice to stay away from dip chips/breadboards/wirewraps and any attempts to put it into real physical world. Taking a build out of a logisim/verilog to real world in chips sucks away all the fun about cpu design - suddenly you have to deal with invisible issues like timing, glitchy half-dead chip, bad wire connection, etc. these are not challenges, just mundane dull work. The only exception to „stay in the sim“ rule is if you want to make an „art statement“, i.e. like BMOW (or my relay cpu https://github.com/artemonster/relay-cpu/blob/main/images/fr... /shamelessplug)

The first image I saw gave me considerable anxiety and dread lol. I am so impressed, and have always wanted to do something like this. I took a digital logic course in university that was an absolute blast. I never wanted to stop there, but ultimately ended up doing so. However, just looking at all those wires made me feel a sense of, "Maybe I won't do this after all."