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Thread: Vintage computer prices.

  1. #21
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    Quote Originally Posted by Hugo Holden View Post
    Are you saying that it contains IC types that have become truly impossible to get and that they are often faulty, requiring some sort of add on patch with non original IC's to get it working?
    I don't know myself how *common* it really is for the RRIOTs specifically to fail, but they seem to have a reputation. (The older Commodore disk drives for the PET used them and they're listed as a common failure point.) And, yeah, what specifically makes them "bad" is they're not just a part that's hard to find an example of because it's obsolete, it's that they were application-specific; you can't just borrow one from your commodore disk drive to fix your dead KIM-1 even though they're both "6530s". The part in question is a multifunction dingus that has some I/O ports, a tiny bit of RAM, and a mask-programmed ROM; they were designed to let you built a minimal embedded device with little more than just the 6502 CPU and the RRIOT. The -xxxx after the 6530 indicates the program that's burned into it; the KIM-1 has half its firmware in each of its two 6530s so it specifically needs a -002 and a -003, each plugged into the correct socket.

    MOS never made a "PROM" version of it, so the only way to replace it if you can't find the original exact mask part is to use the related 6532 RIOT, which doesn't have the ROM built in, on a daughterboard with an external ROM.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  2. #22
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    DAve what is the price for a kit? That looks amazing.

  3. #23

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    Quote Originally Posted by Eudimorphodon View Post
    I don't know myself how *common* it really is for the RRIOTs specifically to fail, but they seem to have a reputation. (The older Commodore disk drives for the PET used them and they're listed as a common failure point.) And, yeah, what specifically makes them "bad" is they're not just a part that's hard to find an example of because it's obsolete, it's that they were application-specific; you can't just borrow one from your commodore disk drive to fix your dead KIM-1 even though they're both "6530s". The part in question is a multifunction dingus that has some I/O ports, a tiny bit of RAM, and a mask-programmed ROM; they were designed to let you built a minimal embedded device with little more than just the 6502 CPU and the RRIOT. The -xxxx after the 6530 indicates the program that's burned into it; the KIM-1 has half its firmware in each of its two 6530s so it specifically needs a -002 and a -003, each plugged into the correct socket.

    MOS never made a "PROM" version of it, so the only way to replace it if you can't find the original exact mask part is to use the related 6532 RIOT, which doesn't have the ROM built in, on a daughterboard with an external ROM.
    Now I see, thank you.

    I seem to suffer from some sort of "spare parts disease". I have to have spares of all the less common IC's in my vintage computers and other apparatus, and at least be able to get the common garden types. I really don't like getting caught out without spare parts. It makes some of those application specific devices a nightmare for me. It is one reason I like vintage computers because they mostly are repairable and usually the IC's are still available.

    I have a Conrac video monitor that uses a vintage Motorola CPU with a UV eprom in it, but because its integral with the cpu, its not possible to read the contents of it out, though there are some theories on how to do it. So I know if it fails its game over for the monitor and there is nothing I can do about it, which drives me up the wall.

  4. #24

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    Quote Originally Posted by VERAULT View Post
    That sounds like a pretty impressive board Dwight. Shame you don't have the plans anymore. I was always impressed by the KIM-1 machines with terminal display outs and cassette drives and all the bells and whistles where it could be used as a standalone computer.
    I have the design. It was just that I don't have plans to make any more. It was just a one time shot to help spread the cost.
    As has been said, the 6530 had a mask ROM that was application specific. These even had the address decoder as part of the mask. The 6530 was also a common chip used for pinball sound generation but at least they were used across several machines with the same mask.
    I believe one can still get 6530 replacement boards from other sources but none are small enough to fit under the 6532 with a small increase in height. Most all the others are a larger daughter boards.
    Dwight

  5. #25

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    The pair of 6530 chips in the KIM are what makes the KIM a KIM. Without those specific parts, with their masked software, you can't have a KIM. Obviously there are workarounds, as have been described, but if one were to try and make a one-for-one copy of a KIM, you can't do it without those two specific parts.

    When I had mine, I managed to shoot 9v in to one of the ports on one them (likely the the A port, I think they each had a single 8 BIT I/O port), sizzling it to beyond "extra crispy", and I bought a spare chip.

    Somewhere, somehow, I actually still have that chip stuck in its anti-static foam. I never installed it.

  6. #26
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    Quote Originally Posted by whartung View Post
    The pair of 6530 chips in the KIM are what makes the KIM a KIM. Without those specific parts, with their masked software, you can't have a KIM. Obviously there are workarounds, as have been described, but if one were to try and make a one-for-one copy of a KIM, you can't do it without those two specific parts.
    You *can* have a computer that behaves essentially identically to one, since the contents of that software is well documented (MOS even published the assembly source), so I wouldn't come down too hard on replicas from a practical standpoint. (I would in fact *highly recommend* that anyone that wants to play with a KIM use one, frankly.)

    I guess at a certain point you get to a slippery slope. For instance, early Commodore PETs that use MOS memory and the first generation of MOS mask ROMs *very* often have to have their memory partially or completely replaced because those chips are failing in droves. (And nothing pin-compatible exists so doing so by necessity involves daughter boards.) I suppose if you're a "collector" that just wants a 100% "authentic" machine that would be a pretty powerful incentive to never play with your first generation PET because, well, if you leave it off forever then you don't *know* if those irreplaceable parts have failed or not. But if you own the machine because you want to play with it the counter-argument is that since it is in fact "fixable* you should be okay if nature takes its course. So... yeah, I dunno. Do you own the machine to use, or to stick on pedestal?

    Usually I'm in the "I own it to play with it" camp myself, but I think if a KIM-1 were to just fall into my hands I would probably make an exception and make it a wall-hanger simply because:

    A: The prices of those things are so crazy, someone's clearly gunning to make them the next Apple I, and:

    B: It's an SBC "dev kit"-class machine, which by definition "playing with it" probably means you're going to want to wire stuff up to it. And the ports you wire stuff up to are directly on those irreplaceable chips, I don't think they're even buffered. I think I'd rather risk smoking the VIA on my Commodore PET, that's a $4 fix.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  7. #27

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    Quote Originally Posted by Eudimorphodon View Post

    I suppose if you're a "collector" that just wants a 100% "authentic" machine that would be a pretty powerful incentive to never play with your first generation PET because, well, if you leave it off forever then you don't *know* if those irreplaceable parts have failed or not. .
    That reminds me of Schrodinger's Cat. It would possibly be better to never look inside the box (Turn the KIM-1 or PET on) and be prepared to face the disappointment that one of those IC's was dead, or alive, or both (intermittent). Let alone play with it and become responsible for the destruction of one of those IC's which would haunt your dreams. Which is actually quite sad, when it appears it was built a lot like a trainer machine to "Play with" and learn.

    I have no idea why a collector would want something like this to hang on a wall, I think the value would be in using it, despite risks and disappointments and need to modify it, if it is just to make investment $ from a "vintage technology portfolio", what a hollow cause.

    I think you are right, the replica is definitely the way to go, all fun and no risk.
    Last edited by Hugo Holden; November 24th, 2020 at 02:01 PM.

  8. #28
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    I think everyone has an item in their collection that they wanted but don't use for whatever reason. Who actually uses an Apple I or does much with an Apple Lisa Twiggy machine?
    What I collect: 68K/Early PPC Mac, DOS/Win 3.1 era machines, Amiga/ST, C64/128
    Nubus/ISA/VLB/MCA/EISA cards of all types
    Boxed apps and games for the above systems
    Analog video capture cards/software and complete systems

  9. #29

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    Quote Originally Posted by Unknown_K View Post
    I think everyone has an item in their collection that they wanted but don't use for whatever reason. Who actually uses an Apple I or does much with an Apple Lisa Twiggy machine?
    I used to be like that with certain things, until I realized that it was completely silly. Leaving this stuff just sitting up is far worse for it than actually using it. As long as you keep every thing maintained and in-check there's no reason to be afraid to use it in my opinion.

    And yes, if I had a Twiggy Lisa 1 and planned on keeping it, I would definitely use it.
    Compaq - “It simply works better”

  10. #30

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    Anyway, if you look at:
    http://www.vcfed.org/forum/showthrea...omputer/page38
    and 39, you'll see the tiny boards I created to replace the 6530 of the KIM-1. Both fit under the 6532 and do add some height but it still looks cleaner than the typical daughter board, normally used.
    There is also a diagnostic board that has a number of test programs on it to check out various parts of the KIM-1. Since the replacement chip uses a EEPROM, the diagnostic board has code to program the EEPROM to be either a -002 or -003.
    A working KIM-1 with an adapter to make a 6532 work is always better than a dead KIM-1.
    Dwight

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