Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucsd!nosc!crash!pnet01!jca
From: jca@pnet01.cts.com (John C. Archambeau)
Newsgroups: comp.os.minix
Subject: Re: Minix virtual memory
Message-ID: <679@crash.cts.com>
Date: 10 Nov 89 03:16:06 GMT
Sender: root@crash.cts.com
Organization: People-Net [pnet01], El Cajon CA
Lines: 30

jerry@altos86.Altos.COM (Jerry Gardner) writes:
>Wait a minute here!  It looks like it's time to clear up a big misunderstanding
>many people have with respect to virtual memory on the 80286.  We've all heard
>all the talk of the 80286 being brain damaged and not being able to support
>virtual memory, but this just isn't true.  What is true is that the 80286
>does not support *paged* virtual memory as the 80386 does.  The 80286 does,
>however, support *segmented* virtual memory.  Each 80286 segment descriptor
>has a present bit and an accessed bit necessary to support virtual management
>of segments.  Granted, it doesn't have a 'dirty' bit to indicate that a segment
>has been written to, but neither does the VAX architecture, and it has gotten
>along fine without it.
>
>Virtual memory on the 80286 is certainly possible (OS/2 does it :-); it may
>not be "child's play", but it certainly is possible.  BTW, I disagree with
>your assessment that implementing Minix VM on the 80386 would be child's play.

Corollary: It's child's play in comparison to implementing VM on an 80286.

As for OS/2, I give more respect to MS-DOS and that ain't much.

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