Close

Finished building ALU!

A project log for TTL 8-Bit CPU better than Z80

An 8th grader designing and building a real 8-bit CPU from scratch using custom architecture and discrete logic.

bohan-xuBohan Xu 02/18/2026 at 01:222 Comments

I finally finished building the ALU part! Here's a picture. The FPGA in the middle does addition, subtraction, complement, and, or, xor, and shifts. The rest off the chips are buffers, comparaters, registers, and the A register. The eight LEDs are connected to the data bus. If you have any suggestions please comment! Thanks!

Discussions

roelh wrote 02/18/2026 at 13:04 point

Hi Bohan, does your ALU also do AND, OR, XOR ? They are important. Perhaps you can get inspiration from my project, the ALU is described here:

https://hackaday.io/project/190345-isetta-ttl-computer/log/217189-the-alu-of-isetta

  Are you sure? yes | no

Bohan Xu wrote 02/18/2026 at 20:36 point

Hi roelh! Yes my ALU does support AND OR and XOR. I’ll also definitely take inspiration from your ALU. Thanks a ton for the link this is super helpful!

  Are you sure? yes | no