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From: waltje@uwalt.nl.mugnet.org (Fred 'The Rebel' van Kempen)
Newsgroups: comp.os.minix
Subject: Re: Multi-segment MINIX
Message-ID: <9105191048@uwalt.nl.mugnet.org>
Date: 19 May 91 16:23:04 GMT
References: <1515@cbmnlu1.cbm.nl>
Organization: MicroWalt Corporation, for MINIX Software Development
Lines: 33

arno@cbmnlu1.cbm.nl (Arno Griffioen) wrote:
> I've been hearing some rumours lately about a MINIX version that can use
> more than one segment on a 286 in protected mode.
Correct.

> Anyone got any pointers? I always heard that it wasn't impossible, but
> that a major rewrite of MM was nessecary and the performance would probably
> suffer (a lot).

Not really.  Currently, MM and the kernel parts of the memory manager
only allocate one (1) segment for code, one (1) for data and ditto for
stack.  Someone in The Hague (nah- won't tell his name here) did a very
good job in changing this.  He used my version of MINIX, and added support
for up to 16 segments (x 3, of course) per process.  He now cross-compiles
a "large" program like my port of Borland MicroCalc II, and converts it
to MINIX a.out (also with a new magic) format. This can be run on MINIX.

The problem is, of course, the compiler.  The poor thing has to decide
when to use inter-segment calls and jumps, and when to use intrasegment
ones.  Same goes for memory ("data") references.

Of course, a call to a function in the same segment is faster than a
similar call to a function in another segment.  Alas, that is the Joy
of a Small iNTEL machine... :-(

The guy I am talking about is planning on a pre-alpha test version by
the end of this month (May, isn't it?).  I will summarize here, although
I doubt his willingness to post the stuff here... more about that later.

Fred.
--
MicroWalt Corporation, for MINIX Development	waltje@uwalt.nl.mugnet.org
Tel (+31) 252 230 205, Hoefbladhof  27, 2215 DV  VOORHOUT, The Netherlands
	"An Operating System is what the _USERS_ think of it- me"