The History of the Commodore ChessMate

by Dave McMurtrie · March 26, 2022

In 1978, Commodore International Limited released the ChessMate. ChessMate was a consumer electronic chess playing device. From all outward appearances, it looked similar enough to many of the other popular consumer electronic devices of the day like Mattel’s electronic handheld football game, but underneath the hood there was a lot more going on. The Mattel games were based off simple calculator technology, while Commodore’s ChessMate had more in common with a computer.

Chessmate’s story began two years earlier in 1976 when a series of intertwined events came together at just the right time and in just the right order.

April 1976

MOS KIM-1

MOS Technology, Inc was a small chip maker based in Norristown, Pennsylvania who had recently begun selling their MOS 6502 CPU. In April, 1976 MOS Technology introduced their KIM-1 single board computer to the world. The KIM-1 was a full computer based around the MOS 6502 cpu that used two MOS 6530 RRIOT chips to provide the KIM-1’s operating system in ROM and to interface the KIM-1 with the outside world.

May 1976

Peter Jennings circa late 70s

A young Toronto man named Peter Jennings was interested in purchasing one of the new home computers that were starting to become popular among hobbyists. In May, 1976 he drove from Toronto, Ontario to Cleveland, Ohio to attend the Midwest Regional Computer Conference where he purchased a KIM-1 computer. Peter became obsessed with writing software for his new KIM-1 and he soon began working on a chess program for the system in his spare time.

November 1976

In November, 1976 Commodore International Limited purchased MOS Technology, Inc. Commodore was primarily a calculator company in 1976 and they were purchasing MOS Technology as part of a vertical integration strategy such that they could make their own calculator chips. Regardless, Commodore continued manufacturing and selling the KIM-1 computers after their purchase of MOS.

December 1976

Peter Jennings and Dan Fylstra at the West Coast Computer Faire in 1979

The chess game that Peter Jennings was working on for his KIM-1 was released as MicroChess and it proved to be exceptionally popular. Over time graphics were added and it was updated to run on other computers of the day including the Commodore PET. For a detailed history of MicroChess written by Peter Jennings himself, visit Peter’s website

The Birth of ChessMate

Commodore International was a fairly diversified company by 1978. They had a semiconductor division, computer systems division, metal products division and a consumer products division. The consumer products division was largely focused on watches and calculators, but they had the resources, expertise and distribution channels in place to take consumer electronic devices to market, and the wild success of Peter Jennings’ MicroChess had not gone unnoticed.

ChessMate Prototype in 1978

Commodore set about to introduce an electronic chess playing game based on Peter Jennings’ MicroChess running on the KIM-1. They hired Peter as a contractor and began working on the device which would be a pared-down KIM-1 with a modified version of Peter’s original MicroChess code in ROM. The ChessMate board was powered by a 6502 derivative, the MOS 6504 cpu. Development of the ChessMate took place in Commodore’s Palo Alto, California facility at 901 California Ave.

As told by Peter Jennings:

The prototype was built by Ray Holt at Jolt from specs I furnished, which was basically an altered Kim. At the time Jolt owed Commodore for 6502 chips and so the prototype was a way of paying. Chuck Peddle, John Feagans and Bill Seiler were involved while I was there. Others may have contributed afterwards.

Peter was not just hired to provide his modified MicroChess software for the new consumer device, though. His role spanned hardware, software, naming and even an attempt at licensing:

I was a hardware guy before I was a software guy. I also came up with the name. We tried hard to name it the Bobby but could not get Bobby Fischer’s endorsement. I did get to spend 3 days playing chess with him in Pasadena, trying to convince him.

An early schematic diagram for the ChessMate confirms that the original name was “Bobby”.

January 1978 Commodore “Bobby” schematic

I asked Peter about his time with Bobby Fischer:

Mostly, he played games against the Kim I had brought with me and I tried to explain why the computer had made the moves it did. After a couple of days he challenged me to a game because he wanted to see how I played. We played 3 games and he won them all, but they weren’t super short. On the other hand, he didn’t look at the board – he was lying on the bed in my hotel room telling me what move to make on the board and then I would tell him my move.