Happy 50th Birthday KIM-1 | Hacker News Reader

Happy 50th Birthday KIM-1

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72 pointsJKCalhoun29 comments

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).

I still hack assembly on my Oric Atmos system, just to keep my 6502 chops fine. The day job has me doing Linux development - somehow its soothing to spend an hour at home winding down on page zero ..

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.

Yes indeed, using the 6502 as a microcontroller, not just a microcomputer, has kept it alive for decades.

You can see similar scope in the 8051 microcontroller, too.

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.

As a 13-year old, I didn’t have an assembler so had to write one first, in BASIC and then eventually in assembler. It was the lack of the thing which made me proficient in building the thing lacking. Plus, my 8-bit machine at the time (Oric Atmos) didn’t have much software distribution in my neck of the woods ..