A very interesting project - YouTube playlist has 22 short videos at present. Here are some details from Mike’s project page:
The plan is there will be approx 320 tubes, specifically 6J6A. As of May 24, 2023, there is one board completed, the sequencer that contains the state flip-flops plus an instruction register latch (just the top four bits), and all the instruction decoding logic. That board uses 80 tubes, which is 160 gates. The tubes just do the inverting, the logic is done by crystal rectifiers. It runs at 28k cps.
Each tube has 2 triodes. A single triode is required to make an AND-OR-INVERT gate. Three tubes (6 triodes) are required to make a D flipflop (ahem, edge-triggered, bi-stable multivibrator). Two tubes (4 triodes) are needed to make a latch.
The tubes are just the processor. For memory and I/O, I use a Raspberry PI. Transistors are used to do the level conversion between the RasPI and the tubes and to drive the LEDs. At some point, I might change the front panel to neons or incandescents with tube drivers, but LEDs will do for now.
When all the boards are done, it will run slower than 28k cps as there will be more circuitry for the bits to work their way through (27 levels of logic for the full processor as opposed to 10 for just the sequencer board). So that implies the processor will come in somewhere around 10k cps, though I wouldn’t be surprised at 5k cps cuz of longer circuit traces.
There’s a little chat in the comments of his Hackaday page too.
With the price of tubes, this could be the last valve new computer out there.
6j6a $3.00 5965 $5.00 (bendix g-15).
Too bad all the valves have been all snapped up the audio hi-fi guys,.
Frank's electron Tube Data sheets tube data here.
Index of /pdf/bendix/g-15