Happy 50th Birthday KIM-1
github.com72 points by JKCalhoun 2 days ago
72 points by JKCalhoun 2 days ago
In 1978, I was at my first engineering job after getting my BSEE. The company had set up a small lab that had variety of small computers, including a KIM-1. It also had an Apple II, a CROMEMCO computer, and a Pet, plus one or two others. At that time, I was only familiar with big iron, like an IBM 370, that I could only submit jobs to. As a result, I was in heaven. Here were computers that I could interact with directly, write programs (in Basic) for, and play games. I was in there every day at lunch or after work, sometimes staying until 2 or 3 in the morning. I messed around with the KIM a bit but found it unrefined and clunky to use as compared to the Apple or even the Pet.
Around 1980, while taking a "Saturday Morning Class" in Toronto - I discovered that there was a lab of ~24 Commodore PET 2001 (8K - blue phosphor, chiclet keyboards) at George Brown College. Spent as much time as I could there engaging with the early hacker community who all brought their shoeboxes of 5-1/4" floppies to trade programs. It was there that I had my first OMG moment when a much older kid showed me his floppy disk catalog program that could sort so much faster than mine did (he used quicksort).
I remember jones-ing for that computer. It was too expensive though. Then I got a series of books about how to build an Elektor Junior, which was a cheaper alternative. I did that, I loved it; and then in short order the BBC Micro stole my heart. The through-line was the 6502, which retains a place in my heart even today. It's fascinating to me that there still remains interest in that CPU even today, with papers and publications and repos. That CPU has had a great innings. Both simple enough and complex enough. It went on to power the Apple, the Pet, various Acorns. It's interesting to look at the family tree, even the ARM chips have a family association (say, cousins through the Acorn line).
The 6502, for all its warts brought the best out in the programmers that used it.
Its low cost and being completely self-contained made the KIM-1 unique among the 6502 computers of the 1970s. It was a small fraction of the cost of an Apple, Pet, Atari etc. which made it practical to build into an embedded controller as if it were just another part.
It did not require an external computer or terminal to use, you could program and run it from the built-in hex keypad. The simple 6502 instruction set did not require an assembler, it was quite practical to write the assembly language program on paper and then hand-assemble it by looking up the hex opcodes -- after a while you remembered the most common ones -- this was actually simpler and faster than dealing with program development tools. It only took a few minutes to key in a couple of hundred bytes, which was sufficient for many control programs -- you were not using the KIM as a personal computer, but as a (much better!) replacement for dozens of TTL chips and IC timers.
You could use it to do real work, build real devices. I built this programmable gas mixer for respiratory physiology experiments:
https://journals.physiology.org/doi/abs/10.1152/jappl.1980.4... Programmable Gas Mixer ..., Journal of Applied Physiology 49(1), 1980.
Couple of blogs about my KIM-1:
1. My 1976 KIM-1 https://blog.jgc.org/2023/11/my-1976-kim-1.html
2. Getting the KIM-1 to talk to my Mac https://blog.jgc.org/2025/02/getting-kim-1-to-talk-to-my-mac...
Thanks. Nice links. I love the handwritten assembler pic with mapping from mnemonics to op codes. If you had to punch it in on a hex keypad, you absolutely needed that. Unfortunately, I never was organized enough to have different color pens :-)
As a high school student I didn’t have the money to buy a 6502 assembler and I used to write my assembly code out in long hand on graph paper, hand-assemble it and type in the hex in the monitor.
Other KIM-1 links some may prefer:
http://retro.hansotten.nl/6502-sbc/kim-1-manuals-and-softwar...
The first single-board computer I had ever heard of. And I saw it in a book on making your own robot (1970's, TAB books, I think). No way I could afford a $400 computer with my measly allowance. Oh well—I've since been able to build a couple replicas.
The author of the robot book [1] had an unusual last name. When I came across the same last name during my time at Apple, a co-worker, I emailed him and he said that it was in fact his brother that had written the book. Small world, I guess.
OMG, thank you for sharing this! I had that book when I was a kid, but couldn't find it again for the life of me. This was the first evidence I had that it wasn't a fever dream.
A buddy of mine and I bought Kim-1 systems. We did all the usual things, abusing the TTY interface to rs232, overclocking the CPU so it could go faster than 9600 baud, hacking Microsoft basic so it would run on the Kim-1
I wrote an interrupt driven cassette data writer to record data while the foreground was doing something else.
The project was to strap a Kim-1 and a cassette recorder to the chest of a skydiver and record their cardiac data after they jumped out of the plane. We wanted to be able to preserve as much of the data as possible should the skydiver go splat. Kind of dark but you know, programming is not all unicorns and rainbows.
Then I did boring stuff like running fig-forth, building my own floppy disc controller and forth block disk drivers. You know, the usual Kim-1 stuff
I nearly bought a KIM-1, but opted instead for the Synertek SYM-1, which had some improved features. It was my first real computer. (I already had a HP-41C.)
I had one of these as a kid, actually on loan from another microcomputer enthusiast. My dad and I had soldered an SDK-85 kit (which I have) and we swapped that for the KIM-1 with another microcomputer enthusiast. It's the machine where I first started to learn programming, in machine code, entered in hex.
There's something really appealing about machines this simple which has been lost in the modern era. But this particular board was very limited, there wasn't a lot you could actually do with it.
The legendary Jim Butterfield needs to be remembered in connection with the KIM.
He wrote the “The First Book of KIM” and it kickstarted his career within the 6502/6510 microprocessor family namely Commodore.
He is such an awesome role model to this day in explaining complex concepts to the average people that made them hungry for more.
Search him on YouTube, you will want to start BASIC on C64 the moment you watch him unpacking a C64 and plugin it in to show how easy it is to write BASIC programs for fun.
The 8-Bit Guy did a great episode about the history of the Commodore PET and it starts with the KIM-1 and how it was basically turned into the PET. Highly recommended!
README looks excessively LLM generated
Yeah this is unreadable trash.
I just don’t understand why people can’t be bothered to take some time to write something by hand about a repo that we’re presumably expected to give a fuck about. Write.
Kim-I emulator and assemler written in T3X/0:
https://t3x.org/t3x/0/sim65kit.html
Calculator:
https://t3x.org/kimuno/kimcalc.html
If you can get microchess and know a little of 6502, you can trivially adapt the ACIA serial code to the I/O of the simulator from T3X.
Also, T3X/0 itself:
thought this might be about kim dotcom -- is he 50 yet?
As a poor engineering student, I couldn't afford one of these, but I could afford the TIM-1 chipset at $35, wire wrapped it up, and borrowed a single-line ascii terminal from a buddy. It's hanging on my lab wall next to other obsolete stuff.
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