Which is based on the 6502-compatible 65C816 but used a simple banking scheme instead of the broken 24-bit address space that chip natively supports (no 24-bit index registers) The way video memory works in it is really clever and lets it really surpass 1980s machines in many ways.
My favorite retrocomputer though has to be
https://www.olimex.com/Products/Retro-Computers/AgonLight2/o...
which is priced right though it doesn't have the keyboard and instead based on the eZ80 which really does extend the Z-80 with 24-bit registers so that you can use all the RAM easily.
