The Coleman Z80 Is a 1970s Microcomputer Designed Using Up-to-Date Techniques

Maker Joshua Coleman is celebrating the holidays with a return to the classics: a 1970s-inspired eight-bit microcomputer, built using modern tools and techniques around a modular RC2014 Zilog Z80-based core.

"It's actually directly based on the RC2014 system," Coleman explains of the Coleman Z80, "but I implemented it in a way that I think you'll find very unique — most specifically aesthetically, but also there are some ways that I designed it that I think make it look kind of more suited to the mid-70s era that I was trying to emulate."

As Coleman explains, the heart of the system is a protoboard reimplementation of the RC2014 — a popular modular microcomputing kit built around a Zilog Z80 or compatible processor. Originally released in 1976 as an enhanced clone of the Intel 8080, the Z80 broke out of its original market of embedded systems and would power some of the most popular microcomputers and home computers of the next decade — from built-it-yourself kits from Healthkit and Nascom to the Sinclair ZX Spectrum, the Osborne Executive, Tatung Einstein, the multi-vendor MSX family, and the Tandy-Radio Shack TRS-80 family.

Taking inspiration from the relatively bulky front-panel-programmed systems of the 1970s rather than the sleeker all-in-one devices which came later, the Coleman Z80 is housed in a laser-cut chassis roughly mimicking an Altair 8800. "I knew I wanted status indicator lights just like the Altair and other front panel systems of the mid-70s," Coleman explains, "[and] furthermore I wanted to evoke the very 'airplane cockpit' design that people like [Apple co-founder] Steve Wozniak thought, correctly, was best to get away from."

A second system housing provides room for additional module boards, including a real-time clock (RTC), seven-segment display module with two different display types, a soundcard, and a speech synthesis module, plus a serial card for communication with an external system. The Coleman Z80 even includes an acceleration coprocessor in the form of an Am9511A Arithmetic Processing Unit (APU) board, which provides faster and broader floating- and fixed-point operations.

More information on the project is available on Coleman's YouTube channel, while source code for the sample programs demonstrated therein has been published to GitHub under an unspecified open source license.