Building a (modern) vacuum tube computer

An interesting project, attempting to build a vacuum tube (valve) computer in the 21st century, implementing the RISC-V architecture.

“Building a vacuum tube computer”

From the project description:

Vacuum tube computers haven’t been built for 50 years, so I thought it was time to do it again.

A design goal is to only use technique from around 1950. That means vacuum tubes for all logic in the CPU, no semiconductors except for crystal diodes (patent from 1906, commercial germanium diodes in the 40’s).

The plan is to implement an existing architecture, and here the conclusion has come to the Berkeley RISC-V. It has only 37 instructions in its RV32I description, is very clean and simple in design and there are test programs and software available.

Another goal is to construct the computer using a cycle time of 1us (1MHz), to get a reasonable speed.

The project starts in August 2013 (nearly exactly 6 years ago as of writing this) with the acquisition of some tubes (valves), the last entry (for the present) being posted in April 2018 and ending abruptly mid-sentence (a bit worryingly so :wink: ).

Found via Hacker News:


Wow, it uses two vacuum tube diodes and a capacitor for DRAM registers – that’s 64 tubes per register! I imagine it’s stalled while he builds a power station. :wink:

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Vacuum tubes (valves) are a good medium for building an accumulator machine… a register-rich machine, not so much. Such a shame though if over-ambition on the choice of machine caused the project to get bogged down.

So, to go under-ambitious, could you do it using just ferrite cores (instead of tubes)?
(Probably not at 1MHz.)

Edit: For example, a SETUN revival project (featuring ternary arithmetic)?

Indeed, as a register file looks a bit like RAM - and you need a solution for RAM too - a small core memory would serve. But note that some microarchitectures need more than a single read-write port, and also note that core memory reads are destructive, so you’d want to design your machine sympathetically.

I’m wondering what’s the simplest machine that has a C compiler… maybe a PIC? Or maybe a C compiler is the wrong thing to be thinking of!

I suspect Al Gore and his disciples showed up with pitchforks and (unlit) torches once he got to a half dozen or so registers :slight_smile:

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No, cores as in cores for switching!

And this is part 1 (introducing the basics of cores) of this mini series:

(SETUN was entirely based on this, but in ternary logic. Not the fastest, but cheap in parts and modest in energy consumption.)

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We need to go help him!

But it’s not as if someone abruptly took the stylus out of his hand. I had a little correspondence with Anders “Ragge” Magnusson and had asked him about it. Today he wrote: “it’s a long-time project, and for the last three years I have been busy with ‘normal life’ . In a perfect world I will be able to continue with it after summer…”

“Usagi Electric” is also working on his vacuum computer for about 2 years now. He has the CPU and some memory ready, but there are still entire boards missing. It takes its fair share of time…

Compare this YouTube playlist.

And Usagi is (sorta) replicating just a 1-bit processor.