Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!batcomputer!cornell!rochester!udel!mmdf
From: leisner.wbst139@xerox.com
Newsgroups: comp.os.minix
Subject: Re: Multi-segment MINIX
Message-ID: <52563@nigel.ee.udel.edu>
Date: 3 May 91 15:37:37 GMT
Sender: mmdf@ee.udel.edu
Lines: 32


I did an implementation of protected mode Minix on a 286.

It basically was a mess.

The C compiler needs to do stuff with multiple segments (I used Aztec as a
cross-compiler, so the compiler really was no problem for me).

The memory manager needs to be changed.

Addresses would need to be extended between applications and kernel to
[segment:offset] instead of just offset.  This would allow things like putting
data (strings) in text instead of always in data.

I basically wanted a model with 64k code, 64k data, 64k heap/stack; which I
found very difficult and incompitable with anything.

The 286 also had bugs (I had my HP analyzer on the socket, was watching the bus
and several things Intel defined between levels of protection didn't work as
defined).

The 286 is basically a bastard machine.  I'd much recommend getting a 386 with
a linear address space and forgetting about segments.  There is far too much
work involved for marginal gain.

marty
(Knowledge is useful in the Information Age)
(Software is mindstuff.  It is the hardest activity created by man)
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