[BBC-Micro] OT PC architecture
jules.richardson99 at gmail.com
Thu Feb 18 13:29:35 GMT 2010
Tony Noble wrote:
> On Thu, Feb 18, 2010 at 1:38 AM, Rick Murray <rick at rs432.net> wrote:
>> I wonder how Unixen worked pre-386? I know a lot of modern Linux-likes
>> won't run on earlier hardware, however the concept predates the
>> introduction of the 386. Was any sort of Unix released for earlier x86s?
> Indeed there was: Xenix. ( http://en.wikipedia.org/wiki/Xenix ). Released
> by, of all people, Microsoft, and later sold to everybody's favourite bad
> guy - SCO.
> It ran on 8088s onwards.
... and almost on the 32016 of the Cambridge Workstation (just to make things
on-topic) :-) The info I've seen leads me to believe they gave up due to I/O
performance reasons long before they had anything like a complete OS, though.
Presumably Unixes of that era running on such lowly processors had no memory
protection at all, so any process could stomp all over any other.
Once upon a time I used to know how to write memory managers for PCs, but I
can't for the life of me recall any details now! A friend and I actually got
reasonably far in writing our own PC OS in the first half of the 90s (inspired
by fledgling Linux and WinNT) - I don't think I have any of the code now,
although I should have design docs somewhere. I miss all that low-level stuff :-)
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