This All-in-One ZX81 Fixes Many of Sinclair's Original Shortcomings

The most popular computer released by Sinclair Research was the ZX Spectrum. In fact, the ZX Spectrum is the best-selling microcomputer in British history and comes close to taking that title for the whole world. But a year before the release of the ZX Spectrum, Sinclair released the ZX81. While there is a lot to like about the Sinclair ZX81, it had many shortcomings. To address those and get a more usable computer, iNimbleSloth built this all-in-one ZX81 based on Mahjongg2's ZX81plus38 design.

The Sinclair ZX81 was a fully functioning computer in an extremely compact package that sold for an outrageously affordable price: £70 assembled, which is £251.76 today (about $313 USD). For many people, the ZX81 provided access to computing that wouldn't have been attainable otherwise. But its performance was poor. It had only 1KB of memory (unless the user attached an expansion module), monochrome graphics, and the worst keyboard you could imagine — far worse than the famously bad ZX Spectrum keyboard. In the United States, we got the got the same computer branded as a Timex.

Mahjongg2's ZX81plus38 design is a modern interpretation of the ZX81 single-board computer PCB that ditches the custom ULA (uncommitted logic array) in favor of ICs that you can actually find today. The ZX81plus38 gives retrocomputing enthusiasts a practical ZX81 platform to build on, and iNimbleSloth ran with it.

The ZX81plus38 is just a PCB, so iNimbleSloth expanded on that to create a complete computer. It has a small 5" TFT LCD screen with a resolution of 800x480, which can accept the composite video signal coming from the ZX81plus38. iNimbleSloth also designed an attractive 3D-printed enclosure and a mechanical keyboard. That keyboard is a custom job with its own purpose-designed PCB and mechanical key switches. It blows the original ZX81 keyboard out of the water and is even better than your average modern membrane keyboard. If nothing else, the upgraded keyboard makes this project well worth the effort for ZX81 fans.

Because the ZX81plus38 can run the standard ZX81 ROM, iNimbleSloth gets access to the full library of software and games. Those are enhanced by the increased memory capacity that this offers, so he doesn't have to deal with the measly 1KB that the ZX81 came with. In addition to the retro games, this lets iNimbleSloth create and/or play new games that might not have even been possible in the '80s.