The Coleman Z80 Is A Modern Take On A 1970s Computer
[Joshua Coleman] likes to design his own computers. Sometimes this means configuring bus architectures, memory cards, and I/O port pins. Other times, he can focus his efforts more on general aesthetics, as well as building a great set of peripherals, as he shows in his latest ColemanZ80 project. Thanks to the RC2014 architecture that defines most of the essential features of a classic Z80 computing platform, [Joshua] was able to design a modern retro computer that is not only truly useful, but also looks like it came off a production line yesterday.
The external design is a sight to behold: bright red laser-cut acrylic pieces form a neat, semi-transparent casing with ventilation slots on the sides and plenty of flashing lights on the front. Inspired by 1970s classics like the Altair 8800, the front panel gives the user a direct view of the machine’s internal state and allows simple command input through a series of toggle switches. The CPU, RAM and other basic devices are housed in one case, with all the expansion modules in a second one, connected to the main board by a 40-wire flat cable.
Although the main board closely follows the RC2014 design, [Joshua] went to great lengths to tune the system for his specific needs. The expansion boards he built include an NS16550 UART to replace the default 68B50, a battery-backed real-time clock, a YM2149-based sound card and even a speech synthesizer module built around the classic SP0256 chip, from Talk & Play fame. An even more unusual feature is the presence of an AM9511, one of the earliest math coprocessors ever made, to speed up floating point calculations. All these modules were built entirely by hand on prototype boards: we can hardly imagine how much time it must have taken.
Output devices include a VGA adapter courtesy of a Raspberry Pi Pico as well as a regular 4-digit 7-segment LED display and a set of classic HP “bubble” LEDs. [Joshua] runs several demonstrations in his video (embedded below), ranging from calculating the Mandelbrot set to playing chiptunes on the YM2149. There is also plenty of room for further expansion: [Joshua] plans to build more peripherals, including a floppy drive interface and a module to drive a robot car.
This is not the first Coleman Z80 computer: the previous version ran on an architecture [Joshua] all designed by himself. We’ve seen several other impressive RC2014 derivatives, such as a tiny micro version and this Altair-inspired case.