Lee Hart
Heath Company was established in 1911 as a producer of airplane kits. After WW2, they switched to producing electronic kits due to the large amount of military surplus electronic components available after the war. “Heathkit” soon became the leading name in electronic kits due to their quality, performance, price, and excellent manuals and documentation. They produced a wide range of products including radios, hi-fi stereo audio, ham radio gear, test equipment, and even color TVs.
The successful launch of the Altair 8800 microcomputer encouraged Heath to design a kit similar to the Altair, but addressing its many obvious shortcomings. This became the H8 microcomputer, announced in July 1977 at a price of $379 in kit form. Thousands were sold, leading many to successful careers in computer science and engineering.
Heath continued to expand and improve on the H8, leading to the H/Z89, H/Z100, and a series of PC-compatibles. Heath eventually went out of the kit business in 1992, when it was no longer less expensive to build your own than to buy cheap offshore products. But many still have a “soft spot” in their hearts for the H8, and they still sell for enormous prices on ebay. A very active user group, SEBHC (the Society of Eight-Bit Heath Computerists – see https://sebhc.github.io/sebhc) is still providing support, parts, boards and accessories for this pioneering microcomputer.
SEBHC members routinely display their Heath computers at Vintage Computer Festivals around the country. But an increasing number of people have never heard of Heathkits! They are completely unaware that it was ever possible to “build your own” radios, TVs, or computers.
So in May of 2026, we came up with the idea of making a NEW “Heathkit” computer. It would be a simplified and miniaturized version of the H8 to re-introduce people to the art of kit-building. It would have the same capabilities and run the same software as the original, with the same high quality parts and excellent “we won't let you fail” manuals that made Heathkits famous around the world.
Description
- 80C85 2 MHz 8-bit CPU
- 32k RAM
- 32k EPROM, or optional 512k flash ROM
- serial port using the 80C85's SID and SOD pins.
- 4x4 keypad using tactile switches
- nine 0.3" 7-segment LED displays
- a PCB styled like a half-size H8 front panel (about 6"w x 3"h)
- powered by USB-serial adapter, or battery operated with three AAA cells
- a manual to imitate the Heathkit manuals
- and, available in kit form NOW at an affordable price!
A goal is to include the H8's PAM8 monitor and BHBASIC. They will need to be patched to run in this minimalist environment, but Heath provided source code for their software to make this possible. An optional flash ROM can also function as a “disk” drive so the CP/M and HDOS operating systems should be able to run. That opens the door to a VAST amount of software as well (like the iconic "your H8 is up and running" demo).
Software
This is very much a work in progress. Our current code is at https://github.com/sebhc/MiniH8
We started with Jon Chapman's “Glitch Works” GWMOM serial monitor for his 8085 SBC mini rev.1, which also uses SID and SOD for serial I/O. That worked like a charm! We only had to patch the baud rate divisor for the H8 Mini's 4 MHz clock, and we had a monitor to read/write memory and I/O, load/save programs in Intel Hex format, and Go to programs in memory. That greatly speeded up development.
GW-MON-80 ROM Monitor
GW-MON-80 1.1 is programmed into the EPROM included in the H8 Mini proto-kit. It supports the following commands. Commands can be typed in upper or lower case. All numbers are hexadecimal. You must enter BOTH digits of the 2-digit data, and all FOUR digits of the 4-digit addresses. You do not need to type the spaces or <CR> at the end of each command.
- D xxxx yyyy Dump memory from xxxx to yyyy...
Ethan Durrant
6502Nerd
Martin Maly
Stephen Willcock
Yep; I did. Thanks for the tip, Mike.