Building a Commodore 64?
ActualDragon wrote 02/20/2020 at 02:46 • 1 pointHey, so don't kill the idea too bad, but in theory (just an idea at this point), how hard would it be to make a commodore 64? Like the schematics are online everywhere, and i know the parts would be hard to find, and im planning on buying a genuine disk drive, but i'm not sure about the software involved. I know it's more than likely a lot more then a stack response would do justice for, but i'm looking for pointers. I've looked through google, but i can't find anyone who's built a commodore 64 based completely from the schematics. I'm not trying to change anything, just build as close a copy as possible. I can figure out the hardware, just wondering about the software.
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You can pick up a used C64 on Ebay for $40. Good source for original ROMs and other custom parts. Yes there is someone that built them and had a lot of success and it's the original factory they'd made a living out of it!
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Odd project, but interesting.
Keep your wire wraps short and the distances between the 6502 and I/O controller as well. The processor was sleepy slow, but scanning ports for changes of state (eg. key clicks) is an exercise that, hand built, will suffer noise and drive you to drink.
Anyway, good luck with the build. It's nicely nostalgic, especially compared to the SBCs you can now snap together for a hundred bucks.
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I've thought about this myself -- build one out of perf, basically. I was gifted a massive pile of Commodore stuff by a close friend, but neither of the two C64s in the pile (breadbin type, no less) boot. Since he has a tech shop, I've asked him to repair one for me, which just needs three DRAM chips swapped out... I don't think he's going to do that any time soon... he's *extraordinarily* busy (see explanation below), and I can't pay him (and he knows) but it's been at least a year now... :-/
Of course I've no skill with the heatgun or I'd've done it myself long ago.
The ultimate problem with building a C64 on a stack of perfboards, at least in my friend's opinion (and the collection, which is quite extensive, basically represents his childhood -- he somewhat literally grew up in front of the things, and he has quite intimate knowledge of them indeed) is that the timing on those boards was done at such an incredibly tight level that getting a perfboard version genuinely functional is essentially impossible. Every fraction of a nanosecond counts -- and if one signal is off by one infinitesimally-small bit of time, whether it's early or late, you could be there with a logic analyzer or o-scope for *days* tracking it down -- and at things quite a bit longer in working out a fix...
...but, hey, maybe it's possible? I dunno. If you actually get up the, er, brass bits to go ahead and try -- I wish you the best of luck, and please PM me so that I know and can +Like/+Follow the project!
EXPLANATION re my pal -- he owns one of three tech shops in town (not counting the guy who works out of a van, and another who only does Mac repairs), but it's by far the best and (almost) everyone around knows it. He is constantly buried in work. Unfortunately, he also has learned (the hard way, and multiple times over) that he really is best off if he works alone, and because he also wants to at least sort of have a life on the side, he generally has enough either stacked up in one corner waiting for attention or walking in through the front door, that he's had a backlog of at least a week as long as I can remember. It's not his fault -- he is absolutely *amazing* at what he does, but being smart with computers and smart with other people don't always go together -- and he is a living example of that. The late Stephen Hawking could understand physics and the nature of the cosmos on a level most of us can't even begin to imagine, but he probably was never very good at, say, tennis... just because someone is smart or "gifted" doesn't mean they know everything -- especially the social stuff.
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Most chips on the C64 are custom Commodore/MOS parts, so there's no off-the-shelf equivalent. You'll need to use NOS or used pulls unless you want to replace some or all of them with an FPGA or micro emulations.
Software... Do you mean software you would need to write to make the pile of chips function like a C64? The only software built into a C64 is in the ROMs. One ROM is the font for the character generator, one is for kernal (like a combination of BIOS and toolbox), and the last is BASIC. You probably won't want to make those from scratch, though you could avoid having to buy originals by using EPROMs or flash. With those the C64 boots into interactive BASIC.
Once you have the ROMs, assuming the rest of the hardware works like a real C64, then it's just a matter of finding applications. Disks, tapes, and cartridges are the media used, and there are hardware emulators for each cheaply available or easily built if you google a bit.
If you don't have any software on media already, and want to run applications pulled from archive.org or the like, you're better off with an emulator. Look for SD2IEC, a 1541 floppy emulator running on an AVR that reads disk images off of an SD card. Even if you have a floppy drive already, this is an easy way to populate blank floppies.
I'd also recommend playing around with a software emulator before you get too far into this project so you have some context.
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I’m not completely sure how it would, or if it would, work, but maybe you could use FPGAs? Again, I don’t know if or how it’d work, but it’d be easier (I think).
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Like this?
https://icomp.de/shop-icomp/en/shop/product/c64-reloaded-mk2.html
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