My4TH homebuilt CPU-less computer

Some new-old retro-computing found via OSNews:

From the site itself:

This page is about My4TH. My4TH (pronounced “my fourth”) is my fourth homebuilt CPU-less computer after MyCPU, MyNOR and TraNOR. I wanted to build the simplest computer possible, with a discrete CPU using as few gates and components as possible, running a Forth operating system.


Ah, a one bit ALU - @Dr_Jefyll will like that!

Data manipulation is done via a single NOR gate on the D0 data line. You may already know that really any logical function can be derived from the NOR function, even complex functions like addition and subtraction. But to process all the bits of a byte, My4TH must loop over all the data bits and process bit by bit. The required data shift function is also implemented as a look-up table in the EPROM.

1 Like

Nice design, that fits on a small card. I am still from the ERA that
uses AOI gates like 7454 or Open Collector like the 7401.
I can see the AGC using NOR gates since back then all you could
pack was about 12 transitors per die.

A nice elegant hack. Truly minimal. The “real” ALU is simulated in software running on the couldn’t-be-smaller “ALU”—the NOR gate. Kudos! Reminds me of the serial-ALU PDP-8/S.

I see that My4TH is now available as a kit from My4TH single board FORTH computer buidling kit… Hmmm.