I built an 8-bit CPU from NAND gates, and it runs Tetris

I just finished a side project I’m pretty proud of: a complete 8-bit CPU built from a single building block, the NAND gate.

How it’s built

From NAND gates I made the basic logic gates, then adders, registers and memory, all the way up to a full CPU. Everything runs in Digital Logic Sim, a free logic simulator, so there’s no hardware to buy.

8-bit ALU (numbers from 0 to 255)
16-bit addressing, so 64K of RAM
800 kHz clock
A small OS running Snake, Breakout, Flappy Bird and Tetris, playable live with the keyboard
The software side

Writing programs in binary by hand got painful very quickly. So I wrote my own programming language and a compiler that outputs the program memory contents directly.

What’s next

I’m thinking about a step-by-step tutorial series on building your own CPU from the NAND gate. Would that interest you? Let me know in the comments!