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From: steve@edm.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: New Dos from Microsoft
Message-ID: <141@edm.UUCP>
Date: Sun, 19-Apr-87 07:42:11 EST
Article-I.D.: edm.141
Posted: Sun Apr 19 07:42:11 1987
Date-Received: Thu, 23-Apr-87 23:52:17 EST
References: <705@imsvax.UUCP> <631@edge.UUCP> <1622@bnrmtv.UUCP> <225@homxb.UUCP>
Organization: Unexsys Systems Inc., Edmonton,AB.
Lines: 20
Summary: SOME things (at least) are faster in real mode.

In article <225@homxb.UUCP>, gemini@homxb.UUCP (Rick Richardson) writes:
> In article <1622@bnrmtv.UUCP>, connery@bnrmtv.UUCP (Glenn Connery) writes:
> > > .... put the '286 into protected mode, the CPU *itself* slows way down!
> > 1) The 286 runs at least 50% FASTER in protected mode than in REAL mode.
> 
> he said that when they went from real mode to protected mode Venix on
> the PC/AT, context switches were 30% faster.

Although context switches may be faster, I understand that actual WORK is
alot more expensive. Namely: changing any of the index registers can take
a LONG time to execute because of having to load new MMU info. 
 This effectively means that the more memory you use, THE SLOWWWEERRRR the
application runs (as a general rule).
 Also:  I understand that Digital had some serious performance problems
getting concurrent PC-DOS running in protected mode.  Can anyone 
comment on this?
-- 
-------------
 Stephen Samuel 
  {ihnp4,ubc-vision,seismo!mnetor,vax135}!alberta!edm!steve