Refurb weekend(s): Commodore/MOS KIM-1 | Hacker News Reader

Refurb weekend(s): Commodore/MOS KIM-1

oldvcr.blogspot.com

46 pointszdw16 comments

I own an original KIM-1 (that shipped on July 27, 1976; revision A, ceramic 6502/6530). See https://imgur.com/a/iCClwCb It works flawlessly. I actually did some programming of the KIM-1 in the mid-1980s for industrial control: https://blog.jgc.org/2013/04/how-i-coded-in-1985.html

That looks nearly identical to my own Rev A. The one I have the prior owner built a small plywood and acrylic enclosure for. It's the original enclosures for these things that their original owners built that really give them personality, like this suitcase unit.

The oldest KIM I'm personally aware of is a original (i.e., pre-Rev A) with a 6502 that still has the ROR bug. I should ask its owner what the date codes on that are.

Interesting. I should write some code for mine and check for that bug. I assume it was fixed by the time this shipped (my CPU is week 21 of 1976). I have an acrylic case for mine to protect it.

You might indeed have one with a bad ROR. My MOS documentation for the time says ROR would be "available" after "June, 1976." The Rev A here is 30th week 1976 and does not have the bug.

Why would one choose to work with a bare computer board atop a layer of tinfoil like this?

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj...

Perhaps the tinfoil was clipped to a ground? Would it then be protected from static shocks and other invisible (to the naked eye) damage?

Historically I've used flattened cardboard outside on top of a brick patio, and ensured I touch a grounded circuit before e.g. replacing capacitors. No e-deaths due to static yet, though my equipment is nearly all from ~circa 1999 or newer, and I believe newer equipment typically incorporates some static protections into designs.

TFA's PCB layout connections are so flowy and beautiful, they remind me of a past HN submission about rounded PCB circuit wiring: "Melting KiCad" https://mitxela.com/projects/melting_kicad / https://news.ycombinator.com/item?id=31108652

p.s. this is an amazing writeup, thank you to the OP for submitting and to the author for taking the time and care. Really, really cool. This reminds me a bit of a Ken Sherriff analysis https://righto.com (!) <3

(author) Thanks! No special reason for the foil other than being a convenient heat resistant shield that can be disposed of so I'm not scattering solder bits around the back room.

The KIM-1 was one of my very first machines, I faithfully lugged it with me across many moves and one day it just disappeared. I still have faint hope that it's somewhere in one of my (too) many storage boxes but I suspect it just got lost. Really a pity because they are becoming more and more rare.

Nice to see this one restored to its full glory. Trying to explain to my kids that once upon a time the full working memory of my computer was a very small fraction of one of the photos they share online was a fun experience.

Note the gorgeous very high quality circuit board.

As for the article: I'm not particularly impressed with the workmanship, as a kid I'd repair boards of this and higher complexity regularly and lifting traces and cutting traces while doing such a simple repair would not normally happen to me. One way to do better would be to use a good quality rework iron with a vacuum pump. Not cheap but if you work on old and nice hole through stuff like this well worth the investment. Otherwise you end up overheating the board. A repair should look more or less as if the board wasn't touched, apart from maybe the gloss on the solder. And make sure to use 63/37 'old fashioned' solder.

It was the first thing I learned to program on. My father went to a conference where they gave him one as swag, and he gave it to my older brother and me. I was, I think, seven years old or so.

Writing code that we hand assembled taught me a lot. It’s probably still in a box at my folks place somewhere in the garage.

I "lost" mine in a move about 40 years ago. I have been in mourning ever since.

(author) Hey now, not all of us are adept at this. I appreciate the tips but we all start somewhere. I was particularly motivated on this one because it's a relatively simple machine that's special to me and I should be able to maintain it.

Hey there, yes, I'm happy you managed to fix it. But you probably would have done a much better job by first practicing IC removal on a bunch of older boards, by the time you can do that with your eyes closed you can practice on the heirlooms ;)

Of course it's yours and you're absolutely within your rights to work on it and your analysis of what was wrong was spot on (and very impressive). But these are getting rare.

I wonder what caused the chip to fail, once in the circuit they are normally quite solid. Keep 'm rolling ;)

I appreciate that. Everything is a learning experience.

I'm told that RAM is a common failure on KIMs, though this was the first one I've personally experienced with my own set.

On mine the LM565 chip had gone, as well as a diode, when I got it from a guy in Almere who worked at the same bank where I worked. That's also the only one that I ever came across here in Europe, there can't have been that many here. I really should make an effort to see if I can find it again.

And yes, everything is a learning experience, I'm pretty sure you'd have a much easier time of it if you did it again. Please do consider getting a proper rework kit, it's well worth it if you're going to do this sort of thing regularly. And in a strange way those skills are getting more valuable again, fewer and fewer people around that can repair vintage stuff. One of my 'side projects' is restoring vintage DX-7's, they're fun to work on and there are enough of them around that even if you buy one that seems to be total junk you'll be able to get another one going and have parts left over.

Fortunately there are a number of KIM-1 replicas for someone wanting to play with an early 8-bit computer but either don't want to pay the high price for an original or don't want to end up worrying about restoration of an artifact like this guy, ha ha.

I have built two replicas now, the most recent was the PAL-1 [1] kit. I also built one from Briel Computers some time ago but his business appears to have disappeared.

The nice thing about the KIM-1 replicas/clones, as opposed to some of the Arduino or Raspberry Pi based ... emulators? .., is of course the real 6502 chip as the CPU.

Also nice about the KIM-1 in general is that the six 7-segment LED displays give you both the address and data at that address at once (and in hexadecimal). Other early 8-bit machines of course displayed data in binary (via das blinkenlights).

(Another clone that looked to be outstanding was made by Corsham Technologies. Sadly the man behind the clone died just a month ago and so those machines have also stopped production.)

[1] https://www.tindie.com/products/tkoak/pal-1-a-mos-6502-power...

[2] https://www.corshamtech.com/product/kim-clone/

(author) Bob's replica unit looked really cool but I never got around to picking one up before his untimely death. It's always nerve-wracking working on a museum piece but this one is very special to me.

Yes, his death is so sad. I wanted to get one of his KIM-1 I/O boards. RIP.

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