6502 Sim http://www.visual6502.org/ From discrete TTL chips https://c74project.com/ A tube version should be feasible. One with Nuvistors would be sweet. With roughly 5000 transistors being replaced by 2500 dual triodes at 6 Volts, taking about 1 Watt of power each, we're looking at abt. 2.5 kW of power consumption just for the filaments. That's a sweet heater in winter time. One 12AX7 with a diameter of 20 mm plus say, 10mm clearance takes up 900mm². If I didn't use the wrong calculator on the web, 2500 of them wold take up 2.25 m² That would fit on a base, e.g. 1 x 2.5 m with some room to spare for interface connectors to the relay based RAM and the cuneiform ROM. Power that shit with two independent arrays of lead acid batteries. Use Knife switches for input and Flak Beamers for output.