A Z80 design of my own, though with inspiration from multiple sources. Goal was to correct shortcomings of a board I designed in '98 and give me an easily-extensible platform on which to run CP/M and tinker. It's modular in the spirit of an RC2014 but not requiring any modules at all for what I considered to be "core functionality".
So far runs as expected and I'm coding away on a BIOS as time allows. If everything works to my satisfaction in the end I may offer some kits on Tindie if there's any interest and if I have time to make a Rev 2 board. This board has 2 bugs requiring 2 jumper wires -- a mis-sized footprint for the coaxial power connector, fixed by drilling, and a system clock trace net that got split into 2 separate nets by a KiCAD typo. There's also bit of physical placement tweaking I'd like to do for practicality.
But it runs like a champ! After the docs and BIOS are complete next up is a mass-storage module (CF or SDD) and getting CP/M on the beast.