> If I put you or OP in a room for a year I highly doubt you could build an 8 bit Atari-like CPU from scratch.

I believe I can, depending on what "from scratch" means. With nothing but transistors, resistors, inductors, coils, capacitors, I can probably do apretty poor general-purpose CPU. Maybe something like a stack-based ISA or, if I had more time, an accumulator-based processor like a 6502, but with an 8-bit bus.

If you're going to ask me to create transistors themselves, well I believe that needs specialised equipment.