This is a simple CPU I made using a ROM to perform addition and hold the state machine. It works on 4-bits at a time to give a 16-bit accumulator.
This machine I made as an experiment in Stack Machine architectures. The system is 32-bit clean.
I wanted full colour on my Apple //c so I put together a small board which converts the output on 15-pin connector to component video. The colour quality was very clear.
I started this shortly after I left school. There's a whole lot more at http://kaput.retroarchive.org/