Commodore Advert - 7th October 1979

As well as the PET/CBM range of computers and the continuation of the calculator line, which had survived the Calculator Wars of the mid 1970s, Commodore wasn't averse to putting out the odd sideline product, such as LED and LCD watches and this - a chess computer.

It was first shown at 1978's CES show and ran version 1.5 of MicroChess, a software version of which also appeared for the Commodore PET.

MicroChess was written by Peter Jennings and by this time was being published by Personal Software, the company that was only ten days away from launching the spreadsheet VisiCalc - the first "killer app" - in the US.

Jennings' company Micro-Ware and Dan Fylstra's Personal Software had merged in 1978, and some of the proceeds from MicroChess helped fund the development of VisiCalc. Personal Software became VisiCorp in 1982.

MicroChess had been written in machine code for the KIM-1, a development board from 1976 that had been built by MOS Technology in order to demonstrate its 6502 processor.

The program, which occupied just 924 bytes, was launched on December 18th, 1976, shortly after it had made an appearance on the cover page of Eric Rehnke's KIM-1 User Notes.

That appearance was thanks to an article by Jim Butterfield - who would become an authority on the Commodore PET - which he'd written after Jennings had met with Butterfield and demonstrated his program.

Due to its growing popularity, which helped make it the first ever game to sell more than 10,000 copies, MOS (now owned by Commodore) agreed in 1977 to ship a flyer for the program with every KIM-1 sold.

Before long, there were enough orders for Jennings to quite the day job and incorporate a new company - Micro-Ware Limited in Toronto - to handle sales and distribution.

In its ten-year run, MicroChess sold several million copies, with the game ending up on Apple, Tandy, Commodore, Processor Technology, IMSAI, Cromemco, MITS and many other microcomputers of the day^[1].

The Chessmate hardware was based upon the KIM-1^[2], but with a 6504 processor. This processor was smaller than its more-famous 6502 cousin, and was virtually identical to the 6507 as used in the Atari VCS/2600 games console^[3].

Jennings had initially wanted to call the hardware "Bobby", in honour of Bobby Fischer, but couldn't get Fischer's endorsment - even after spending three days in Pasadena playing chess, whilst trying to convince him^[4].

It retailed for £59.95 - about £430 in 2025, and it was particularly popular in West Germany^[5].