The Z20X Open Source Computer Blends Vintage Computing with Modern Design

Building a computer today could be as simple as connecting an HDMI monitor, keyboard, mouse, and USB-C power supply to a small board. But, back in the late 1970s and early 1980s, the process was much more involved, requiring reading datasheets and soldering components together. Konstantin Dimitrov blended these two computing experiences, creating the Z20X open source computer. It resembles a computer from the past but can be built entirely from modern hardware.

At the Z20X's heart is a 20 MHz eZ80 with 128 KB of Flash RAM, 520 KB total RAM, and 4 MB of non-volatile storage. Unlike the computers from the 8-bit heyday, there is also a real-time clock, a 7.0 TFT display, an SD card slot, PS/2 connectors, and a YM2413 programmable sound generator.

Dimitrov explains his Z80-compatible processor decision:

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.

The venerable 8-bit Z80 powered several early home computers like the TRS-80 and Sinclair Spectrum. Today the Z80 core is still actively used in many applications! Engineers use them as an IP core in FPGA designs or in embedded application-specific ICs. Zilog, the original manufacturer, produces chips that you can still buy! The Z20X is not using an actual Z80. Instead, it uses a variant named the eZ80, which is backward-compatible with the original Z80's instruction set.

While the above picture shows an expander board, the Z20X can operate without it. The main card houses the CPU, PS/2 keyboard and mouse interface, an LCD, and the 72-pin expansion header.

There is nothing exotic about the 4-layer PCB. So, your favorite (4-layer capable) PCB manufacturer should be able to fabricate it with the freely available Gerber files. For those who want to develop a case for their Z20X, there is an STP file of the PCB available to make enclosure design easier.

While it does not appear that you can purchase an assembled Z20X, its website contains a bill-of-materials (BoM). Except for the LCD and the Yamaha sound chip, you can source all the components from popular component distributors like Avnet or Premier-Farnell.

For more information, check out this site for the Z20X documentation.