Microchess Remembered

Playing chess has always been a bellwether for computers. The game isn’t trivial, but the rules are managably simple. However, the game is too complex to be easily solved entirely, so you have to use tricky software to play a credible game. Big computers do have an advantage, of course. But Microchess — arguably the first commercial game for home computers — was able to play on tiny machines like the Kim-1. [Joachim Froholt] interviewed [Peter Jennings] — the man behind Microchess to learn the whole story of its creation.

In 1960, [Jennings] was ten years old and had to persuade the local librarian to let him read adult books on electronics and computers. Five years later, a ham radio teletype and some circuitry helped him practice chess openings and was the first of many chess-playing machines he’d build or program.

Microchess itself took six months of painstaking programming, entering hex codes into the computer. Word leaked out from a user’s group meeting (where Microchess beat a human player), and [Jennings] was swamped with requests for the program. In late 1976, the program was offered for sale as a teletype listing or, for an extra $3, a cassette tape.

The program went on to be very successful and moved to other platforms. Commodore even made a special dedicated device based on the Kim-1 to play Microchess, a piece of hardware unique enough that [Michael Gardi] honored it with one of his phenomenal replicas.

A Portable KIM-1

The KIM-1 was the first computer to use the 6502, a CPU that would later be found in the Apple, Ataris, Commodores, and the Nintendo Entertainment System. Being the first, the KIM-1 didn’t actually do a whole lot with only 1k of ROM and a bit more than 1k of RAM. This is great news for anyone with an Arduino; you can easily replicate an entire KIM-1, with a keypad and 7-segment display. That’s what [Scott] did, and he put it in an enclosure that would look right at home in a late 70s engineering lab.

The impetus for this build was [Scott]’s discovery of the KIM-Uno, a kit clone of the KIM-1 using an Arduino Pro Mini. The kit should arrive in a few weeks, so until then he decided to see if he could cobble one together with parts he had sitting around.

Inside a handheld industrial enclosure is an Arduino Uno, with a protoshield connecting the keypad and display. The display is an 11-digit, seven-segment display [Scott] picked up at a surplus shop, and the metal dome keypad came from a hamfest.

Getting the software working took a bit of work, but the most important parts are just modifications to the standard Arduino libraries.

Now that [Scott] has a KIM-1 replica, he can program this virtual 6502 one hex digit at a time, run Microchess, or use the entire thing as a programmable calculator.