[BBC-Micro] OT PC architecture

Jules Richardson 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 :-)

cheers

Jules





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