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Recreation of a Sinclair ZX81 (dual rom 80/81) based on Grant Searle’s project.

The Sinclair ZX81 was my first computer, I learned how to program (in basic) using this machine in late 80’s. It’s a master piece of simplicity and ingenuity. Of course, the ZX Spectrum brought colors and sounds but even the ZX81 had expansions like Chroma and Zonx. I believe that every hobbyist who would like to learn how to develop their own projects should start by studying this machine as it presents a simple and easy way to understand a computer architecture. … and… yes… that’s exactly what I did :)

I started designing retro computers in January 2021. It all started because my first computer was a Microdigital TK82C (a clone of the Sinclar ZX81).

I learned to program on it and had so much fun programming simple ascii games. I missed my little friend and would like to still have it with me… Well… during pandemics, I was chatting with a friend via Zoom and told him my story… He had his ZX81 and gave it to me. Of course, after many years over the closet it wasn’t working.

Since I couldn’t use it, I started to study the ZX80 and ZX81 schematics to learn how it works and try to fix it. Then, after reading Grant Searle’s page, I realized I could create my own clone. \o/ Yey… and my ZX81? I could fix it later. :D

This led me to study other computer architectures and then I started to create my own projects…

The eagle files and gerber I used were created by Wilco (Alejandro Valero). But there are some changes I made to improve the sensitivity of the cassette and another one that I had to do to fix the video output.

I’ll update the eagle files asap to add them but the mods are already in my schematics. I also sent some suggestions to Wilco and He added to his post on his blog.

For now, I’m working on Baffa-2 Project but I have plans to create some peripherals like zonx (soundboard clone shown on video bellow), sdcard reader, vga video output, etc.”

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