Z20X is a simple expandable DIY computing system, built around the eZ80 microprocessor. I chose eZ80 due to its native simplicity and full backward code compatibility with the great and very popular Z80 and Z180. The design goal of Z20X is to offer a good DIY/LIY (Do-It-Yourself/Learn-It-Yourself) kit for system built with through-hole components, simple enough for assembly and learning in deep details, but without the constraints of using only old technology ICs. In order to maintain full exposure to technical details, the system also avoids using secondary MCUs or programmable logic, and sticks only with true hardware solutions.
eZ80F92 running at 18 MHz (default on board)
128 KB flash ROM (internal for eZ80)
520 KB total RAM on board (512K external plus 8K internal)
4 MB non-volatile storage (optional, can be upgraded by changing the IC)
SSD1963-powered 7.0 inch TFT display with resolution 800 x 480 pixels
It turned out there were some things which required immediate fixing. The two expanders has their main connector inverted on the PCB! Of course, there is a way around, but it is much cleaner to have it in the right way.
The main board had some header holes too small. I must have changed those by mistake since they were fine in the previous version of the board. Anyway, fixed those too. Also, the crystal frequency is (finally!) set at 18.432 MHz.