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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: 2, Informative) by darinbob on Friday February 21 2014, @07:18PM
I had always thought this was the early Sun-1, however it appears this used a custom designed MMU. Sun-2 used 68010 and again with a custom MMU.
A big problem with 68000 was that some exceptions could not be restarted after an interrupt, which is where the trick of using two CPUs in parallel came from. One would be cycle or half cycle behind and then be halted if the earlier CPU detected a fault. I can't discover what computers actually used this technique though but it's been talked about for decades.
The 68010 fixed this problem and added some privileged instructions, and was pin compatible. However it wasn't only slightly faster so most companies just waited for the 68020 instead.
So I don't know how the Sun-1 really managed this with only one 68000. I suspect there were some operations that just couldn't be recovered but it could do enough to run System 7.