Friendly fZ80 design and construction

05 Apr 2026

The machine is contained on a single PCB containing hardware to support a full-featured CP/M machine with every peripheral support device I could think of.

MP/M was intended as a way for many people to share one computer; Digital Research was surprised to see instead use by a single user, to do multiple things on the same computer. fZ80 is designed for this latter "off label" use. To this end fZ80 has a build-in window manager; you can switch between and resize windows ("consoles") at any time with keystrokes.

SD card technology replaces floppy disks and hard disks both. Much of CP/M's "work flow" is built around the concept of removable media; a removable SD card "floppy" is 8 megabytes, and multiple built-in hard disks reside on one high-performance micro-SD card inside the machine. MP/M gets its own, additional, 32-megabyte disk drive. File interchange with modern machines is designed in.

Required but not included: a modern keyboard with USB interface; compact "60 percent" keyboards are fine. A display, likely modern LCD, capable of 1024 x 768 resolution, with a VGA interface, or an HDMI to VGA adapter, not provided. You must provide a USB power supply capable of 500 mA (nearly any).

How

The host MCU is a Teensy 4.1, a 600 MHz ARM CPU, from PJRC emulating an NMOS Zilog Z80 and peripheral components (disk interface, serial and parallel ports, etc). However, 100% of the fZ80 software is 8080/Z80 assembly language and BDS C 1.6, written on the machine itself using CP/M and MP/M programs and tools. This provides a close to idealized "1980" experience using the machine.

There exists USB support. At the moment only a keyboard is supported, but it works with a hub and more devices are possible.

The innards of the machine are now documented in the Operator's Manual (see the Docs page at the top.)

Kicad files for the printed-circuit and parts assembly

I have to bundle them up and make a web page. I intend to put everything here. If you bug me it may happen sooner.

All works here unless otherwise specified are copyright 2026 by Tom Jennings. Permission is granted for personal use with no remuneration. Corporations or any organization or their agents, employees, consultants or other relationships human or otherwise, expressly prohibited without written permission.