KevinSep 18, 2025

Figuring out the TD4 4-bit DIY CPU made from logic chips...

https://emalliab.wordpress.com/2025/09/18/td4-4-bit-diy-cpu/

#TD4

TD4 4-bit DIY CPU

I was looking for DIY CPU projects, as I like kits that help me think at the lowest level of processing. It helps keep me grounded in how far technology has come over the years. Some of the options…

Kevin's Blog
Show threadKevinSep 27, 2025

My TD4 kit has arrived.

And wow, that really is a lot of diodes...

#TD4

Show threadKevinSep 28

It works! That was a great build :)

Details here: https://emalliab.wordpress.com/2025/09/28/td4-4-bit-diy-cpu-part-2/

#TD4

Show threadKevinSep 28

A simple 4-bit "Larson Scanner" - just a sequence of OUT instructions and a jump.

https://makertube.net/w/gwjtRveafD98M4PdqEcaoR

#TD4

TD4 4-bit CPU "Larson Scanner"

PeerTube
Show threadKevinOct 1

And now with some notes on programming and some example programs.

BTW - Anyone think of a way to multiply two numbers given only two registers and no other storage...?

https://emalliab.wordpress.com/2025/10/01/td4-4-bit-diy-cpu-part-3/

#TD4

TD4 4-bit DIY CPU – Part 3

Having now spent some time thinking about and building my TD4 4-bit CPU this has a look at some code that I can run on it. Part 1 – Introduction, Discussion and Analysis Part 2 – B…

Kevin's Blog
Show threadKevinOct 5

Now with added bling! Part 4 has some simple hardware mods that add LEDs in some useful places to help debugging.

https://emalliab.wordpress.com/2025/10/05/td4-4-bit-diy-cpu-part-4/

#TD4

Show threadKevinOct 29

Returning to this for a moment, this is my own PCB with built-in bling!

https://emalliab.wordpress.com/2025/10/29/td4-4-bit-diy-cpu-part-5/

#TD4

Show threadKevinOct 29

https://makertube.net/w/beyW1XWnp4dfxkXhFWfhhm

#TD4 #4bit

Kevin's TD4 4-bit CPU

PeerTube
Show threadKevin

And here is my PCB alongside the original.

#TD4 #4bit

Oct 30 at 8:42amWeb