I bought my first TTL data book in 1979. I was learning 6502 machine code at the time and dreamt of building a simple TTL CPU. I sketched some circuit ideas; but that was as far as it went. Now, 25 years later, I've finally done it! Working evenings and weekends, the Mark 1 took a month to design, 4 months to build and a month to program. Here's the result: