@ernie the first home computer I used was Z80 based. It was a cool and baroque instruction set and had a neat set of auxiliary chips for things like I/O. I even breadboarded a robot using one plus a Z80 PIO combined with a kids R/C tank and a home brew motor controller. There was a 256 byte static RAM chip that I programmed from another Z80 machine. It had a habit of rebooting due to some electrical interference problem #noshielding. Unfortunately the Z80 itself is not visible in the photo