68 Katy – 68000 Linux on a Solderless Breadboard

http://www.bigmessowires.com/2014/11/17/68-katy-68000-linux-on-a-solderless-breadboard

125 29 11 years ago

Reminds me of the old PT-68K board; loved that thing, and the 68K.

farmdve• 11 years ago

This is amazing, as a newbie in electrical engineering and just recently playing with my Arduino this is simply awesome!!

Narishma• 11 years ago

Previous discussion: https://news.ycombinator.com/item?id=8622720

tunesmith• 11 years ago

Followups since this was posted in November: http://www.bigmessowires.com/category/68katy/

CamperBob24• 11 years ago

God watches out for drunks, fools, and people who build multi-MHz logic circuits on solderless breadboards. :-P

From a signal-integrity perspective, he should not be able to get away with that.

a13692099932• 11 years ago

fools, and people who build multi-MHz logic circuits on solderless breadboards

I think you may have just repeated yourself there.

CamperBob24• 11 years ago

I guess it's not really any scarier than 80s-era wire wrap prototyping, at the end of the day. Still, my hat's off to him just because he had the guts to try it!

He should send it to an FCC/CE test lab as an April Fool's joke.

pkaye• 11 years ago

I think he is running it at 2MHz which should be doable.

mutagen• 11 years ago

I 'helped' a labmate troubleshoot a simple oscillator circuit in the 2 MHz range on a breadboard by turning my circuit on and off. Despite not designing any antenna-like features it was broadcasting enough to get his marginal circuit into oscillation.

noonespecial• 11 years ago

Was thinking the same thing. Especially with his "Schematics... forget it; organic creation" blurb. There's as much luck as wire in this build.

File it under "bet you can't do that twice in a row".

wumbernang4• 11 years ago

I've built commercial designs using that approach no problems at all. Most of my crap is built on PCB blanks and I have to spend some time reverse engineering it after I'm done.

Picture straight off my bench: http://i.imgur.com/AyXNHfX.jpg

Animats2• 11 years ago

He can't. "My 68008 runs at 2 MHz (it was unstable when tested at 4 MHz), providing similar performance to a 1 MHz 68000." He had to de-rate the clock speed of an 8MHz part to get it to run on that breadboard.

The 68000 line has a sad history. It came out in 1979, and for a while, it looked like it was going to be the winning microprocessor. Intel didn't have a 32-bit entry for years later. But early attempts to build workstation machine ran into problems. The 68000 had no matching MMU, and wouldn't work properly with an MMU anyway - page fault state saving wasn't quite right. Machines with external MMUs were built anyway, but great kludging was needed to get around the design flaw. The Apple Lisa avoided using increment instructions, and Apollo had two CPUs; one for the user and one for the kernel, with only one running at a time.

That was fixed in the 68010, which came out in 1982. But by then, IBM had picked the Intel 8088 for the IBM PC. Motorola didn't come out with the MC68451 MMU until a few years later, and it was a slow, segment-oriented MMU. So the Macintosh didn't have an MMU, and had a much weaker OS than the Lisa - no process isolation, no paging, not even a real CPU dispatcher. The UNIX workstation crowd (Apollo, Sun, HP, etc.) all developed their own MMUs for the 680x0 line.

If Motorola hadn't had those errors in the 68000 and had shipped an MMU earlier, the history of computing could have been quite different.

jdswain• 11 years ago

Looking back it does appear that Intel did nearly everything right, and their competitors didn't. It did help a lot though getting the IBM PC business, and due to that, aligning with Microsoft. If you look at the 68000 machines at the time they all had flaws that prevented them from really taking off, often not things that couldn't be corrected, but things that held them back. The Mac didn't have a hard disk, or multitasking, or color. The Amiga would always be constrained by the custom chips and that would be a problem long term, plus Commodore wasn't investing enough in software. Atari had a good simple product, and GEM wasn't too bad, but they didn't develop it further either. And the workstation market was constrained, as said by the parent, by the lack of a decent MMU solution. And then RISC came along too. In an alternative universe maybe the 68000 machines could have joined forces around a common unix platform and built a major market, but that didn't happen here.

kayamon• 11 years ago

That was fixed in the 68010, which came out in 1982. But by then, IBM had picked the Intel 8088 for the IBM PC.

Wait, that doesn't make sense - the 8088 didn't have an MMU either. Why would that have affected IBM's decision?

wumbernang4• 11 years ago

Seriously it's completely fine in the digital domain if the boards are relatively new, aren't crap (i.e. are Wisher/3M boards without those awful phosphor bronze contacts) and you're under about 10MHz and have enough decoupling capacitors and keep your signal paths relatively short. I've built pretty much this machine and it was frequency stable to about 8MHz and it only died after that because the clock was divided down from a 32MHz XO.

Stray capacitance isn't a mega problem unless you're doing analogue and require frequency stability or going above ~10MHz. The killer for digital is usually ringing on the high/low state transitions but if you look at the timing charts for most things this isn't that bad. Most digital stuff works pretty well if the signals are pretty fugly.

However, wave a scope or logic probe near it and all sorts of crazy shit can happen.

source99• 11 years ago

Reminds me of 18-545 at CMU. We did it with wire wrap though. Good times.

Congrats on being able to fit the kernel in 512K

ramgorur• 11 years ago

when ls -l /bin is being typed, all the last modified dates are "Jan 01 1970" why ?

jacquesm• 11 years ago

Because they are read as '0' and that's the start of the unix epoch.

biturd• 11 years ago

Would mac os 9 apps compile and run on this system?

68 Katy – 68000 Linux on a Solderless Breadboard

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