I've just run into this, which I think will appeal to forum members. Someone has built a microprocessor out of individual transistors, soldered to boards and mounted in racks. They're also linked to LEDs so that it's possible to see what the processor is actually doing. The project is not for the faint-hearted - it's taken nearly two years, about £40,000 of components, and probably a lifetime's worth of soldering. But it's now running, and the builder can play Tetris on it.
Full details are on the
Megaprocessor's own website.
