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Finished building ALU!

A project log for BX-8

Homebrew 8-bit TTL CPU, generation 2 of an ongoing series toward running Linux.

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

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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!

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