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From: dkyoon@pollux.usc.edu (Dae-Kyun Yoon)
Newsgroups: comp.windows.ms
Subject: Re: Performance degradation in 386 enhanced mode
Message-ID: <29402@usc>
Date: 18 Jan 91 20:08:30 GMT
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a752@mindlink.UUCP (Bruce Dunn) writes:

>     On some machines, but not all, tasks running in 386 enhanced mode are much
>slower than in standard mode.  This can be seen by using the computational
>index from the Norton Utilities in both standard mode and 386 enhanced mode.
>It can also be seen for some programs such as the Microsoft Flight simulator,
>which become extremely sluggish in 386 enhanced mode but are ok in standard
>mode.
>     This problem has nothing to do with swap files - disk access is not
>involved in demonstrations of the problem.  The problem has nothing directly to
>do with memory size - the performance difference occurrs between two different
>modes on the same machine with the same memory.
>     There seems to be some correlation with the speed of machines - one report
>has stated that the problem occurrs on 16 MHz machines but not on 20 MHz
>machines.

I agree that the performance degradation in 386 Enhaced mode has *almost*
nothing to do with swap file.  And it also has nothing to do with the
speed of the machine.  Of course, if the machine is faster, the performance
in 386enhanced mode is better than on the slower machine.  However
we are talking about the relative performace degradation between standard
mode and enhanced mode on the same 386(386sx) machine.

The performance degradation in 386 enhanced mode is the result of
multitasking of windows applications even a DOS app is running with
exclusive box checked.  In standard mode, if a dos app is 
activated, all other apps including windows apps are suspended.
However, in enhanced mode, windows apps are always able to get a
time slice of CPU.  You can easily verify this by doing file transfer
using one of the windows comm program (like winqvt), and focus on the
DOS app which is supposed to be run exclusively.  You will see, the
file transfer's going on in background.

I would appreciate any comments on my observation, and pealse correct
me if I am wrong.

-- 
Dae-kyun Yoon
dkyoon@usc.edu, ..!uunet!usc!dkyoon