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From: jpp@slxsys.UUCP (John Pettitt)
Newsgroups: comp.unix.xenix
Subject: Re: 386 Unix/Memory Models
Message-ID: <222@slxsys.UUCP>
Date: Tue, 13-Oct-87 09:25:34 EST
Article-I.D.: slxsys.222
Posted: Tue Oct 13 09:25:34 1987
Date-Received: Sun, 25-Oct-87 20:50:56 EST
References: <143@conexch.UUCP> <140@turnkey.UUCP>
Reply-To: jpp@slxsys.UUCP (John Pettitt)
Organization: Specialix Systems Ltd, London, U.K.
Lines: 45

In article <140@turnkey.UUCP> jack@turnkey.CTS.COM (jack) writes:
> . . . . . . Also, there is only one memory
>model, large (all segment registers, and hence pointers are now 32 bits wide).
>So there will be no more need to fool with makefiles to determine
>which memory library to call for. I assume this will also be the case with
>packages such as 386/ix from Interactive or Microport's release (whenever it
>becomes available).
>
There are several memory models in 386 Xenix - small model (4GBytes),
large model (in the doc but not compiler passes ?) and 286 (-M2, runs
the 286 compiler passes).   ISC 386 (and therefore microport ?) seems
to default to the Intel 386 small model (4 Gbytes).   

The Xenix 386 small model code for most of the benchmarks I have 
run is about 30 to 40 % faster than the 286 version on the same
hardware (Dell/PC Limited 386 in our case).   There is little or
no advantage to the ISC/ATT compiler over the M'soft/SCO version,
but I have been told that the greenhills C is very much faster. 
Xenix 286 bin files run about 10% slower under 386 Xenix 
than 286 Xenix on the same system.  

We have had ISC 386 and Xenix 386 running here for some time now 
and both systems perform well with few bugs.  The performance of
both is spoilt by the silly system defaults chosen.  We run 8+
user boxes with lots of ram and the real throughput can be 
boosted by a significant factor by adding I/O buffers and other
tuning.   The settings supplied with Xenix 386 are far too low for
an 8+ user box - they are in tune with a 1.5MB 2 terminal system.


FLAME PROOF SUIT ON
The new Compaq 386/20 with Xenix 386 or ISC V.3/386 appears to be as
fast (or faster ?) than many so called mini computer systems in most
real user applications.  (I have run 16 Uniplex II users on one - 
If you have used Uniplex you will know what I mean :-)
FLAME PROOF SUIT OFF

Before the flame starts we run Xenix 286 & 386, Microport 286 and ISC
V.3/386 systems in house and the *company policy* is to be os independant!


-- 
John Pettitt G6KCQ, CIX jpettitt, Voice +44 1 398 9422
UUCP:  ...uunet!mcvax!ukc!pyrltd!slxsys!jpp  (jpp@slxsys.co.uk)
Disclaimer: I don't even own a cat to share my views !