Assembling a computer is relatively simple these days, yet some enthusiasts choose the more difficult route and build them from scratch, including their logic. We've covered creations like the Mega-Processor and the MOnSter 6502 before, but today's example is even more extreme: a 1-bit computer built with vacuum tubes, inspired by Motorola's MC14500 industrial controller.
There are many ways to learn about computers. We can drown in manuals, datasheets, and technical details, take an old machine and experiment with it through modifications, or build them… one component at a time. That path is hard, costly, and fundamentally slow, but some enthusiasts follow it with determination, creating wonderful things.
One such enthusiast is David, better known as Usagi Electric on YouTube. A little over a year ago, he began working on a 1-bit computer built with vacuum tubes, and after 22 episodes (averaging 18–19 minutes each), he reached the conclusion for the processor. Ideally, you'd watch the full series, but in the last video, David does a great job presenting an overview:
Building a 1-Bit Computer with Vacuum Tubes
The project is inspired by the MC14500 industrial controller developed by Motorola. This chip began making its rounds in 1977, with the goal of replacing relay systems and other programmable logic controllers. David's version includes specific improvements, including an upgrade to the MC14500's basic logic unit, turning it into an arithmetic-logic unit. He also admits to cheating a bit by using two silicon diodes, but some vacuum tube computers used them, limited to very special cases.
The vacuum tube chosen by David was the 6AU6, widely available, reasonably priced, and compatible with reduced voltages. It's not hard to imagine a circuit with hundreds of volts when talking about vacuum tubes, but this 1-bit processor uses +24 and -12 volts (as a comparison, the IBM 603 uses +150V, +75V, -100V, -175V, and -250V). The hardware demonstration starts at minute 11, but what we see there is only 25 percent of the project. It still needs three additional modules: program control, RAM, and input/output.
Official site: Hackaday.io - Source: Hackaday
