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posted by
LaminatorX
on Friday February 21 2014, @01:33AM
from the I-don't-care,-I'm-still-free.-You-can't-take-the-garage-from-me dept.
from the I-don't-care,-I'm-still-free.-You-can't-take-the-garage-from-me dept.
demonlapin writes:
"Brian Benchoff at Hackaday has an ambitious new project: a homebrew computer based not on a classic 8-bit processor like the Z80 or 6502, but on the 16-bit Motorola 68000. It's a backplane-based machine with wire-wrapped connections planned. His first summary post is here. Blinkenlights are planned."
[ED Note: With so much commercially available hardware getting more and more locked down, projects like this are a good reminder of what is possible for a dedicated enthusiast.]
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Homebrew 68000-based Computer Build
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I'm not a robot like you. I don't like having disks crammed into me... unless they're Oreos, and then only in the mouth.
-- Fry
(Score: 1) by pixeldyne on Friday February 21 2014, @05:50AM
What was the limitation of the 68000? Because I ran bsd quite comfortably on an 020 (no mmu) with 2mb ram.
(Score: 2, Informative) by Uncle_Al on Friday February 21 2014, @11:40AM
Apollo DN100
There were two 68000's. When the first page faulted, the second cleaned up
the fault and restarted the first.
(Score: 0) by Anonymous Coward on Friday February 21 2014, @02:13PM
Animats posted on an old (similar) article that the 68000 didn't do instruction backout properly. Not sure how that works, though.
(Score: 1, Informative) by Anonymous Coward on Friday February 21 2014, @02:55PM
I believe Unix needs a MMU to run properly. The 68020 was the first m68k with a MMU chip, and the 68030 was the first to have the MMU on-die.
(Score: 2, Interesting) by Uncle_Al on Friday February 21 2014, @03:16PM
> I believe Unix needs a MMU to run properly. The 68020 was the first m68k with a MMU chip, and the 68030 was the first to have the MMU on-die.
68000 unix machines were built, using designs including variations of the "SUN" MMU design or the Moto 68451
You just couldn't do demand paging with the 68000 because you couldn't restart an instruction.
(Score: 0) by Anonymous Coward on Friday February 21 2014, @06:33PM
> I believe Unix needs a MMU to run properly.
As other people have mentioned, uCLinux can run on a 68000 [eetimes.com] without an MMU!
(Score: 1) by darinbob on Friday February 21 2014, @08:23PM
Yea, but that's not really Unix. And I'm saying that as someone who believes Linux is Unix.
Basically you're left without memory protection; which doesn't really make something non-Linux by itself.
However you are unable to dynamically grow the size of heap or stack for processes. So like Minix you either allocate a standard stack size for everything or you specify a specific stack individually for each process. All memory is shared, everyone presumably allocates from the same heap, etc.
(Score: 0) by Anonymous Coward on Friday February 21 2014, @09:02PM
> Yea, but that's not really Unix. And I'm saying that as someone who believes Linux is Unix.
True. But given the limitations of the 68000, I would rather run something Linux-like than System 7-like. If you can't have memory protection, you might as well have preemptive multitasking!