Join us as we discover the story of Microchess for the KIM-1, one of the first commercial home computer games ever published.
Article written by Joachim Froholt
Do you know what the first commercial game for home computers was? Much has been said about the first arcade and console games, but when we turn to the realm of computers, information becomes far less accessible. What is commonly known is that in 1977, three computers were launched: the Apple II, TRS-80, and Commodore PET. Together, these are often called the «trinity of 1977», and they revolutionized the market by making computers something anyone could own and use.
It was on also these platforms that the budding computer games industry began to take shape. However, to find the first commercial home computer games, we have to go even further back in time.
Primitive machines
The first computers sold for the home market were introduced several years before the «trinity». These machines were entirely different from what we think of as a computer today, and were typically sold via mail-order as kits the buyers had to assemble themselves. The first on the market was the Altair 8800, which came out in 1974. If you bought one of these machines, you did not get a keyboard or screen; instead, it had a front panel with switches and LED lights. You programmed it by flipping switches, and the response came in the form of blinking lights.
The machine could be expanded with equipment that made it marginally more useful, but you wouldn’t be an early adopter of the Altair 8800 unless you were very fascinated by the new computer technology and likely also had a deep interest in electronics in general.
In 1976, another early machine was released: the KIM-1. This system is interesting for many reasons, one of which being that it was made by the microchip manufacturer MOS Technology and ran on their own 6502 processor, which later ended up in everything from the Commodore 64 to the Nintendo Entertainment System. But it was probably also on the KIM-1 that the first commercial home computer game was released.
The KIM-1
Before we go into detail about the game itself, a brief description of the KIM-1 is in order. The KIM-1 didn’t have a screen but instead used a seven-segment LED display like you’d find on an old calculator, with room for six individual characters. The keyboard was similarly calculator-like – it had 24 buttons, including the numbers 0 through F (we’re talking hexadecimal numbers here) and eight other buttons for system use. It didn’t have an operating system as we think of one today; you would turn it on and start entering machine code to give instructions.
The computer came with 1 kilobyte of memory, meaning it could hold approximately 1,000 bytes. Each byte represents a number between 0 and 255, with its own memory address used to refer to its contents. I’ve written a bit more on how this works in another article (in Norwegian).
But how on earth could someone program and use a machine with such absurd limitations compared to what we think of as a computer today? In short, by manually filling the memory with instructions and data in the form of hexadecimal numbers. One memory address at a time. You can try playing with a KIM-1 simulator online to see for yourself.
Fortunately, it was possible to connect additional equipment like a printer terminal, cassette player (for storing and loading programs), extra memory, and even a monitor. The game we’re going to discuss didn’t require any of these; instead, the manual explained how users could program support for a screen or printer terminal if they had one. In fact, for the first versions of the game, users had to enter the program code themselves. It was printed in its entirety in the manual, and once entered the users could then save the game to a cassette if they had the means (otherwise, they’d have to repeat the process each time the machine was turned on).
With all this in mind, it might be surprising to learn that the game we’re talking about today is something as complex as a chess game with a functioning and relatively competent computer opponent. The game is called Microchess, and it was developed by British-Canadian Peter Jennings in 1976. We’ve been fortunate enough to have him help us share the full story of Microchess, so grab a cup of coffee or hot chocolate and enjoy some real gaming history.
An early interest in computers
Peter Jennings was born in Bedford, England, in 1950. His mother came from one of the countries that were occupied by the Soviet Union after World War II, and was what was called a DP in the postwar era. According to Jennings, she faced discrimination in the UK, and wished to live somewhere else. Meanwhile, Canada was actively seeking new immigrants. So the family moved to the Canadian city of Kirkland Lake in Ontario in 1957.
In the 1950s and 1960s, computers were not something most people knew much about, but Jennings quickly became fascinated by these electronic brains and the possibilities they offered.
– My first memory of computers was reading about them predicting the outcome of the 1960 United States election of President Kennedy. Perhaps I had heard of them before, but I don’t know. Something about that fascinated me and I tried to learn as much as I could about them, Jennings tells us.
This meant a trip to the local library, where he had to obtain «forbidden» knowledge:
– I pestered the librarian at our local library to let me read books from the adult section (I was 10 and we weren’t supposed to stray from the children’s books). I found some introductory information. I was already very interested in electricity and electronics, so I built myself a simple «computer» with relays, switches, and lights that played a number guessing game – the computer guessed the number you were thinking by asking questions. Later I built an analog computer using potentiometers and meters that I used to predict the next election based on early results using historical information I had incorporated from the newspaper.
Programming on paper
But it wasn’t possible for an individual to buy a computer at that time, and Jennings wasn’t one of the lucky ones with access through work or school. That didn’t stop him from learning how to program:
– I learned Fortran from McCracken’s book [a guide to Fortran programming from 1961]. With no access to a real computer, I wrote programs and debugged them by single stepping through the lines myself.
This meant he already knew what he was doing once he got the chance to test a real computer:
– My first access to a real computer was at the University of Waterloo. There was a school trip by bus, 150 kilometers, and we got to punch cards and write simple programs. My first program was to create a reference table of transmitter frequencies for different crystal frequencies for my ham radio. It was very handy. I learned the power of the computer as an assistant.
In addition to his interest in computers, Jennings, was as you might guess, an avid radio enthusiast, and he also developed an early interest in chess. Again, it was through books that he learned the game:
– I learned to play chess from an encyclopedia. Later when I was in high school I joined the Chess club and played after school. I also played over ham radio and by post in those days.
So it was only a matter of time before he began thinking about combining chess and computers:
– I remember reading an article in Scientific American about a computer that could play chess. There was a page of example ALGOL code for some of the analysis. I can remember studying it for hours trying to understand what it was doing. I saved that article for years.
He then started experimenting:
– In 1965, someone gave me an old World War II surplus teletype machine to connect to my ham radio. I was trying to learn more chess openings and I thought it would be helpful to build a «computer» that would play with me to study openings. I used a tape recorder, a homebrew modem, and some logic to build a «computer» of sorts that would play openings with me. That was my first chess playing machine. I continued to dream of building a real chess computer some day.
Starting a business
In 1972, Jennings earned an MA in physics from Stony Brook University, and in 1974 he followed up with an MA in business administration from McMaster University. He wanted to start his own business related to computer technology, but he wasn’t sure exactly what he should focus on. So he took a job in the sales department of a company called Comshare, which sold financial planning packages as well as a programming platform called APL. Although he worked in sales, he had access to the company’s computer and was allowed to use it after work hours – something he took advantage of.
It was at this time that he returned to his dream of a computer playing chess. The first chess games on mainframe computers appeared as early as the 1950s, but now was gradually becoming feasible for people to actually buy a computer themselves. And Jennings went systematically about figuring out which of the available machines that would fit his plans the best.
– I knew it was possible to make a chess playing game with a big computer. When microcomputers appeared in the early 1970s, I thought it might be possible with a microprocessor. I wasn’t sure which microprocessor would be better. I had access to a Xerox Sigma 9 at work, and programmed simulators (in APL) for the 8080 and 6502 in order to test some algorithms for chess. I decided I liked the architecture of the 6502 better. The KIM-1, at $250, was the first computer I could afford to buy – we were still paying off our student loans.
As you probably realized from the introduction of the KIM-1, the idea of creating a real chess game for that machine is, to put it mildly, an ambitious one. Jennings explains:
– I was confident that I could do it, but it was a crazy confidence, because it was only based on my dreams and not on any analysis of the problem. From the beginning, I wanted to create a program that was good enough to sell as a product. I also dreamt of starting a business and this seemed like something I could do with limited resources.
We have also mentioned that programming on a KIM-1 was, well, clunky.
– The Kim-1 has a hexadecimal keypad and a 6 character display using 7 segment LEDs. It is a very basic implementation of a 6502 with input and output and 1K of memory. Although there is an interface for a terminal, I didn’t have one until later, so all input was by pressing opcodes into the keypad.
An ‘opcode’ is a machine code term for a number that represents a command, essentially something the processor should do (like adding two numbers together). This is even more cryptic for us humans than Assembly code, where such commands have slightly more helpful names like ADD. Jennings continues:
– The actual creation of the program was done mostly by writing source code and translating it into opcodes manually, looking them up in the Reference Card for a while, but by memory later. I still remember most of them. I can write simple programs from memory today: A9 00 85 23 …
It was a time-consuming and ‘manual’ process:
– Much of the coding was done by hand [on paper]. All of it was entered into the Kim-1 through the hexadecimal keyboard. I did write an assembler I could use at work, but when I got home, all of the changes were made by hand assembling the source code changes into hexadecimal opcodes and typing them in.
For the chess programming itself, Jennings again relied on literature:
– A lot of the rules for the strategy were based on Aron Nimzovich’s book, My System. The book, complete with yellow highlighter on the important parts, is still on my shelf.
It’s not enough to know the rules
Getting the computer to play chess in an adequate manner was a long and demanding process. After all, it wasn’t enough for the machine to understand the rules; it also had to evaluate potential moves, weigh them against each other, and find the best ones. So even when it learned to make only legal moves, they rarely made much sense. But Jennings didn’t give up. Night after night, he worked on playing his game. Every time it made a mistake or an obviously bad move, he stopped the program, examined the rules and evaluations that had led to the poor choice, and modified the code. Then he restarted the process.
– There were a lot of all-nighters. I would spend hours playing games against the computer, then analyzing what caused each mistake, adjusting the code, and starting again.
For part of the work, he dug out his old teletype machine, a Model 15 Teletype from Teletype Corporation. This model was introduced in 1930 and became something of a standard model for the U.S. military during World War II. Thus, Microchess is likely one of the very few video games where equipment from the 1930s was used during its development. On his website, Jennings talks a bit about what that experience was like:
– When running, the Model 15 made a thundering noise as the head klunked across the page, typing letters one by one. To save us from eviction, it sat on a 12 inch thick foam pad, which lessened the transmission of vibrations to the floor below. The smell of hot machine oil and ozone filled our apartment when it was printing.
Not quite like modern game development, in other words.
The world learns of Microchess
As Jennings mentioned, his plan was always to launch Microchess as a commercial product and thereby establish his own company. KIM-1 had relatively limited sales numbers compared to later machines, but the people who did own one were quite enthusiastic about their machine. In July 1976, American Eric Rehnke started publishing the newsletter KIM-1 User Notes, which provided an opportunity for KIM-1 owners to learn about what other users were doing with the machine. A community also formed around the newsletter, and through it and Rick Simpson at MOS Technology, Jennings discovered there was another KIM-1 enthusiast in Toronto. His name was Jim Butterfield.
Butterfield was, like Jennings, focused on pushing the machine to its limits, and it didn’t take long before the two connected. One evening, Jennings brought an unfinished version of the game and met with Butterfield and a few other enthusiasts. They set up a chessboard to test the game. It was a milestone. Microchess played against a friend of Butterfield’s, and after a close match, the game launched an attack on the opponent’s king. On the next turn, it had the player in checkmate, and Microchess had defeated its first human opponent outside of Jennings.
The experience clearly made an impression on Butterfield, who ‘leaked’ the story to Eric Rehnke. Microchess immediately became the hot topic in the next issue of KIM-1 User Notes. Despite the magazine containing no contact information for Jennings, he immediately began receiving phone calls and letters from people curious about how they could get hold of the game.
The development of Microchess took about six months, and the game was released on December 18, 1976. This makes it one of the first home computer games professionally sold as an independent game and not, for instance, as a part of a book. Though initially, it was indeed published in text form. Users received the manual, which included the game’s entire code printed on the back. So at first, publishing the game was more like releasing a magazine – although, of course, this was before desktop publishing and similar systems made the process easier. The tools used was a typewriter and correction fluid, and for the game code itself, the old Teletype Model 15 did the job. As the game gained traction, users were offered the chance to get a cassette copy for just three extra dollars.
And the game did indeed gain traction. After its release, Jennings continued working for Comshare during the day and handling Microchess orders in the evenings. But one day, when he came home to the house he had just moved into and noticed that the postman had seemingly forgotten two bags of letters on his doorstep, he realized it was time to quit his day job. Because when he after much deliberation decided to take a peek into the bags, he discovered that all the letters were addressed to him. The bags contained a small fortune in Microchess orders and checks.
So Microchess wasn’t just one of the first commercial home computer games ever released, it was also the first home computer game to surpass ten thousand copies sold. «Everyone» who owned a computer wanted Microchess. With it, they had something to show off – a tangible thing their otherwise somewhat useless machine could actually do, and which others could easily understand. This wasn’t programming, maths or some other obscure thing, it was playing chess! Jennings believes this was one of the reasons for the game’s success.
– I think the timing was right. There weren’t many ways to show off your little computer, and Microchess played a role in justifying the purchase to your spouse in a real way.
It helped that the people who bought it loved the game:
– And it was just plain fun to play. I can’t remember even a hint of a negative response. Everyone was amazed that their computer could play chess. The people who visited our booth at the little computer shows were so full of gratitude and enthusiasm it made all the effort worthwhile. I loved the idea that I was making so many people happy.
Playing Microchess
How is Microchess to actually play? Well, if you’re not the type who can play chess blindfolded, you’ll need a chessboard and pieces, or at the very least, pen and paper. Without relatively expensive additional equipment, such as a terminal, the KIM-1 can’t show you the situation on the board; it can only tell you the computer’s moves. So you’ll need to handle the visualization yourself. Additionally, the calculator-like display can’t name the squares on the board correctly. Instead, they’re labeled from 00 to 77. The same goes for the pieces—they are labeled from 00 to 0F. Again using hexadecimal numbers. The manual includes the necessary diagrams:
Using an example from the manual: When the display shows 0F 13 33 after the computer (white, in this case) has made its move, it means it moved the king’s pawn (0F) from square 13 (its starting position) two squares forward, to square 33. Or, in traditional chess notation: E2-E4.
If you were one of the lucky ones who had your machine hooked up to a screen or, more likely, a printer terminal, you could add the required code and get a visual representation of the board after each move. In that case, the game could be played without extra tools, although the board would still not be «interactive» as we think of it today. This was a common way to play computer games in the 1970s – Microchess appeared around the same time as text adventures like Colossal Cave Adventure and strategy games like Star Trek were popular on mainframe systems.
Many versions of Microchess
As mentioned earlier, Microchess was ported to several platforms, including many that are forgotten today. The first, however, was the aforementioned Altair 8800, which ran on Intel’s 8080 processor. For this platform, the game was originally sold on paper tape, a further development of the punched card concept used with old mainframes. Today, it’s absurd to think that commercial games were sold as rolls of paper with holes punched in them, but that’s how it was. A fledgling Microsoft sold its first product, Altair BASIC, in the same way at around the same time.
– The 8080 version was a direct line by line translation of the 6502 version by Terry O’Brien. He had an Altair with a DEC terminal with a paper tape punch and reader. We worked on it together until it played identically to the Kim-1.
In 1977, the Apple II, Commodore PET, and TRS-80 computers were released to the market, followed by platforms such as Atari 8-bit. Although they had varying features, they all shared one thing in common: they were significantly more user-friendly than the KIM-1 and Altair 8800. As a result, the market expanded dramatically in a short period, and, of course, the game appeared on all available platforms.
– After I expanded my Kim-1, I worked on improved versions of the program. As I recall, Brad Templeton worked on the PET and Atari versions. Andy Kamienski worked on the TRS-80 version. In general they did the user interface and the chess code was all mine. They worked for me at Micro-Ware in Toronto.
As this happened, the computer games industry was swiftly becoming a real industry:
– [In the beginning,] the industry was small enough that we could send an ad to every computer store in the world and expect a purchase order by return mail. Life was simple back then. My life changed when Radio Shack placed an order for 20,000 cassettes for the TRS-80.
Of course, these later versions of the game are a lot easier to play than the original, featuring graphics and a better user interface. But what if you want to play Microchess today? Which version should you go for?
– I guess Microchess 2.0 for the Apple II was the last one I wrote. Microchess for the Radio Shack CoCo has the same engine, which I translated for the 6809. I don’t know if it matters about [what version] being the best, as compared to today’s chess engines it is so primitive in many ways. I still think that part of the commercial success of Microchess was that it was beatable and made stupid mistakes, just like an amateur human player. It was fun to play and win or lose.
From Microchess to Personal Software
This is where we bid farewell to Microchess for this article, although the story continues on Jennings’ own website. Microchess formed the foundation for Commodore Chessmate, a chess computer launched in 1978. The story of Chessmate involves figures such as the powerful and ruthless Commodore boss Jack Tramiel and the highly eccentric American chess legend Bobby Fischer, so it’s definitely worth reading.
Peter Jennings did not create any other games besides Microchess, but he gained an important position in the emerging software industry through Personal Software, considered the first independent publisher of software and games for home computers. There, he helped release several games developed by others and worked on the groundbreaking spreadsheet program VisiCalc. He recounts:
– I played different roles at different times. From founding partner, Chairman of the Board, and what today would be called CTO as the company grew. But I never stopped coding and still haven’t. Like all small startups, we all wore all the hats and rolled up our sleeves to get things done. I did not program any other games myself. Micro-Ware and Personal Software both published games by other authors. We began the idea of a software publisher bringing products to market.
Becoming a software publisher was a natural progression for Jennings, who truly believed in the future of computing:
– I always understood the way that a computer amplified personal abilities and thought everyone should have access to one. I wondered if selective memory had retroactively created a false memory of believing in the future of microcomputers. But then someone pointed out an op-ed I wrote in Wharton magazine in response to Byte Editor, Carl Helmers, proclaiming that personal computers would always be a hobbyist technologist niche.
Jennings disagreed:
– By early 1979, I expected software to make personal computers usable by everyone for banking, communications, and education; transforming the use of computers into a way of life by the end of the 1980s. It was only a few months later that The Source and Compuserve began connecting people by email and online discussion groups as well as facilitating downloadable software. The world was about to change very rapidly.
But what about chess?
You’d perhaps think that after his history making chess games, chess would remain a big part of Jennings’ life. This didn’t happen, though, in fact he virtually lost all interest in the game after completing Microchess:
– My chess playing days ended in university, where I reached my maximum skill level playing at the North American University Championships. After that I didn’t have time for chess. Programming Microchess actually ruined my game because I was paying so much attention to what the computer was doing, and since it was for testing, I was avoiding taking advantage of the weak parts of the algorithm. It changed the way of my own thinking. So, after playing Bobby Fischer in 1978, I didn’t play against another human or computer for many years.
But things have been gradually changing lately:
– In the past few months, the Google algorithms have been suggesting YouTube videos to me by Anna Cramling and GothamChess and enticing me with clickbait videos about Magnus Carlsen losing to a child, etc. I ended up watching a few and have been drawn back to the game. I find watching the rapid analysis very interesting. It must be so different for players learning the game today. There are so many resources and the ability to practise endlessly against extremely good engines makes serious training available 24/7.
He notes that the way chess is typically played has changed greatly since the seventies:
– I see that blitz play is now the norm, and that makes sense. We would occasionally play blitz games in the old days, but it was not often. Playing 5 minute games seems to fit today’s zeitgeist of instant gratification and TikTok videos. I find myself drawn to wanting to play again. I should download an app or find some humans who are interested. Sadly, the days still only have 24 hours.
Jennings isn’t interested enough to have any opinions about today’s players or the AI-based chess engines that can, to some extent, be considered the modern generation of Microchess. However, he greatly appreciates the interest in old computers and highlights 6502.org as a vibrant community where people can experiment with and program on these vintage systems. He is also grateful for the continued interest in Microchess:
– It always warms my heart to see people still interested in the old games and getting pleasure from playing them and reading about them, he concludes.
We are grateful that Jennings took the time to answer our questions, and for his patience during the work on this article.
- Further reading (in Norwegian): Historien om El Ajedrecista, en over 100 år gammel sjakkspillende maskin
It is possible to play Microchess on a modern Windows-based machine, using a KIM-1 simulator called Soft6502. You can download it from the official site, and follow the instructions from Peter Jennings’ site (under the Kim-1 Simulation subheader). The experience is … interesting. It feels a bit like solving a puzzle in a Myst-like adventure game, where you use the available information to figure out what buttons to press. And it’s appropriately satisfying when you interpret the answer you get, and see that it makes sense. But to complete an entire game this way might not be tempting in a world where Chess.com is a mouse click away.
While Spillhistorie.no is a Norwegian site, we do have some English language content available. For instance, if you are interested in the early history of computer games, we can reccommend our feature on the history of Rogue, where we interviewed Glenn Wichman, as well as our interview with Don Worth, creator of Beneath Apple Manor.
If you enjoyed this article, please consider supporting Joachim Froholt on Ko-Fi.
This article is also available in Norwegian.
Required legal information on the photo of Paul Stein and Nicholas Metropolis playing chess against MANIAC: Unless otherwise indicated, this information has been authored by an employee or employees of the Los Alamos National Security, LLC (LANS), operator of the Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396 with the U.S. Department of Energy. The U.S. Government has rights to use, reproduce, and distribute this information. The public may copy and use this information without charge, provided that this Notice and any statement of authorship are reproduced on all copies. Neither the Government nor LANS makes any warranty, express or implied, or assumes any liability or responsibility for the use of this information.