VCF East 2021: Preserving Heathkit’s 8-bit computers

To say the name Heathkit is well known to Hackaday readers would be an understatement. Their legendary kits have launched countless electronic hobbies and ultimately many careers. From relatively simple radio receivers to oscilloscopes and televisions, the company offered kits for all skill levels from the post-war period through the 1990s.

So it’s no surprise that in 1977, seeing the success of early personal computers like the Altair 8800 and IMSAI 8080, Heathkit decided to join the fray with its own computer kit. But by then, the home computing market had begun to shift from a hobbyist pursuit to something the whole family could enjoy. Compared to the Apple II and the TRS-80, both also launched in 1977, Heathkit’s machine seemed like the product of a bygone era.

While it may not have gained the notoriety of the microcomputers it was designed to compete with, the Heathkit H8 is certainly not forgotten. Tucked away in a corner of Vintage Computer Festival East 2021 was an impressive exhibit dedicated to the Society of Eight-Bit Heath Computerists (SEBHC) called Heathkit: Keeping the Legacy Alive. Brought to you by Glenn Roberts, this collection of original, modern hardware demonstrated the incredible effort that this group of passionate Heathkit owners have gone to to not only preserve the memory of these often overlooked computers, but to continue to improve the kit’s unique design.

Not just a clone

Although the Heathkit H8 may have been designed as a contemporary of the Altair 8800 and used the same Intel 8080 processor, it was by no means a clone like the IMSAI 8080. In perhaps the greatest A departure from common microcomputers of the time, the H8 did not use the S-100 bus. Hastily assembled and based on military surplus 100-pin edge connectors, the S-100 bus had a number of known issues, so Heathkit decided to design a simplified 50-pin backplane design which they have called the Benton Harbor Bus.

Installing the H8 backplane

The backplane was mounted on the right side of the H8 case and accommodated ten angled expansion cards. The first slot was naturally occupied by the front panel hardware, with the CPU board occupying the second. In the default configuration, this left a generous eight additional slots for expansion purposes, although the last card had to be of reduced length or it would hit the power supply.

Operationally, the H8 also differed significantly from its competitors. The front panel removed the Altair’s distinctive binary toggle switches and LEDs, and replaced them with an octal keyboard and seven-segment LED displays. This allowed users to enter programs much faster and examine memory addresses, although noting the addresses was somewhat less intuitive. That said, the H8 actually had a 1KB ROM that contained enough code to boot the machine into a working state, so the user didn’t have to grab a loader every time it booted like they would on the older S-100 microcomputers. .

Obviously, Heathkit wasn’t just looking to copy what the competition was doing. They had some very interesting ideas for how a microcomputer should work and made a number of improvements over the de facto machines of the time. But there is always room for improvement.

Remastering a classic

Since the H8 came in kit form and included complete schematics, SEBHC members were able to create modern replicas that roll in various tweaks and upgrades. With community developed PCBs and documentation, it is possible to create a working Heathkit H8 without having the original hardware.

An H8-2000, with IDE drive and ATX power supply.

Depending on the generation of PCBs you are using, these are referred to as H8-2000 or H8-2020 by community members. Without the benefit of the original enclosure, these machines can end up looking rather industrial, but the aesthetics largely depend on how far the person building the system wants to go. Of course, if you’re lucky enough to have an original H8 (or at least parts of one), you can augment it with the newly developed components and extensions for the best of both worlds.

SEBHC members such as Norberto Collado have developed an incredible range of expansion cards to fit the H8, such as memory upgrades, IDE controllers, network interfaces, a USB controller that supports mass storage devices and even a new CPU board that uses the Z80. A properly outfitted H8 has the potential to be a retro computing dream machine.

Glenn placed two of these H8s at the head of the table to catch the attention of passing attendees, because even to the uninitiated it was abundantly clear that these computers were the result of mixed design. Seeing the vintage cases fitted with modern ATX power supplies and newly made expansion cards, viewers couldn’t help but be curious. Particular attention has been paid to what Glenn calls “Big Blue”, an H8-2020 equipped with a surprising blue LED display and an illuminated keyboard, a beautiful blend of 70s simplicity and modern style.

Copy contest

In an effort to catch up with newer machines like Apple and Tandy, Heathkit soon introduced a new desktop machine, the H89. It was based on the Z80, combined a 12-inch CRT display and disk drive into a single unit, and was available in both kit and pre-built form. The end result was something very much like the TRS-80 Model III, and nothing like the H8 that preceded it.

Sitting right next to Glenn’s table, Alex Bodnar brought in his gorgeous H89 as part of an exhibit he titled Adventure 1.0 on the Heathkit H89. As the name suggests, his machine was configured to run the CP/M version of the text adventure from the original diskettes offered by the Heath Users’ Group.

Unfortunately, Heathkit’s days in gaming were numbered. Shortly after the release of the H89, the company was purchased by Zenith, who in turn renamed the H89 the Z-89 and ended sales of the kit version. The Z-89 underwent a few revisions and remained on the market until 1985, but the Heathkit name would never again appear on a computer’s front panel.

For a new generation

Although Heathkit is an exceptionally well-known brand among electronics enthusiasts, relatively few know of their brief foray into the computer market. Several participants left Heathkit: Keeping the Legacy Alive surprised that a company they knew so well had developed and marketed several computers they had never even heard of.

The Heathkit H8 might never have had a chance to play alongside Matthew Broderick in the 1980s, but thanks to the efforts of the Society of Eight-Bit Heath Computerists, this vintage computer seems well placed for a second chance. in life. The fact is, you can build an all-new H8 today that’s better performing and more reliable than the 1977 original. So whether you’re looking for a one-of-a-kind electronics project or want to explore the world of retro computing, a Heathkit could be just What are you looking for.