The Valve.Computer is an 8 bit computer, with the usual 12 bit address and data buses plus the rather unusual current demand of over 200 Amps. It can play a decent game of PONG using its valve and relay RAM, or run a 32 bit Fibonacci sequence using modern NVRAM. After switch on you have to wait a while for the last thermionic valve to warm up. If you look from the side you see a few start to show a red glow.

After visiting Bletchley Park, it occurred to me that several thermionic valve computers had been rebuilt, and now run in museums, but that no new design of a valve computer had been constructed in over 50 years. The thought of building one seemed ridiculous, but I wondered if a modern design could overcome the issues of size, power and the very real danger of high voltages.

source: HN