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From: martyl@rocksvax.UUCP (Marty Leisner)
Newsgroups: comp.os.minix
Subject: protected mode minix
Message-ID: <188@rocksvax.UUCP>
Date: Thu, 30-Jul-87 17:18:44 EDT
Article-I.D.: rocksvax.188
Posted: Thu Jul 30 17:18:44 1987
Date-Received: Sat, 1-Aug-87 11:03:47 EDT
Organization: Xerox: Henrietta, NY
Lines: 55

I've seen some news traffic on talk of implementing a protected mode Minix
system on PC ATs.  Anyone making any headway on this?

In order to do it, I need to resolve some issues.
1) Is there a way to differentiate between the different hard disk 
controllers for the different ATs?  I want to be able to boot a system
with one hard disk driver -- or at least a driver which gets configuration
information from someplace.  I've saved some messages about various controllers
I've seen on this news group -- is there any definitive answer about these
hard disk controller boards??  I'm only using genuine IBM ATs of various 
vintages.

2) I've spent a few days playing with the 80286 to get it to run in 
protected mode.  Seems I understand what's involved now.  I'm planning on
using Aztec C to recompile the kernel -- is what I'm using and I understand
its code generation.  I've seen some discussion about using MSC -- but the
major reason I don't like msc is no source code for the libraries.  At 
least with Aztec I can quickly compare the source between the Minix source and
the Aztec source.  

3) Anyone have an MS-DOS emulator?  It should be very straightforward to map
a number of functions through interrupt 21 to the Minix kernel -- a large
number of functions (open/close/seek/read/write) all have nearly identical
meanings in DOS and Unix.  The emulation doesn't have to be perfect -- it just
has to be enough to do something useful (which means no direct video calls
necessary -- if the program doesn't expect to talk to stdin/stdout/stderr,
forget it).

4) Has anyone done anything with ethernet on Minix?

5) I'm planning on handling all exceptions in an intelligent manner --
if I feel like it I may also do things like copy on write after fork.  I'm
not yet sure whether to build it up as a 2 layer system (user/supervisor) or
a 3 layer system (user/file system/security kernel).

6) I may look at some Xwindows concept.  I definitely want some type of
windowing built in.

My major motivation to use Minix is I want a protected mode file system and
memory manager which I have source code for and works.  
My target system is going to have to support a reasonable amount of 
concurrency and be used in a real-time environment requiring millisecond
resolution -- what I currently see is something that on a 1 khz interrupt
(no kernel mode?) to execute real time control. 

If I ever have a change to do it, I'll put out the modified sources.

Once I start to change things, I don't guarantee anything.

Comments/questions/criticisms welcome.

marty leisner
xerox corp.
leisner.henr@xerox.com
martyl@rocksvax.uucp