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From: a752@mindlink.UUCP (Bruce Dunn)
Newsgroups: comp.windows.ms
Subject: Performance degradation in 386 enhanced mode
Message-ID: <4491@mindlink.UUCP>
Date: 17 Jan 91 13:49:50 GMT
Organization: MIND LINK! - British Columbia, Canada
Lines: 34


     From recent responses, it is apparent that there is some confusion about
the problem which is being experienced.  The basic problem is as follows:

     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 have the problem on a 16 MHz 386 (not a 386 SX).  I wonder if the
problem is because my memory above 1 megabyte is not on the motherboard, but is
on a memory card on the bus which can only be accessed at bus speed.  My
hypothesis is that when run in standard mode, Windows runs mainly in the 1
megabyte of easily accessible memory on the motherboard, but when I ask for
enhanced mode much more use is made of the memory which can only be accessed
through the bus.       Would people who have the problem please mail me
information on whether their memory is all on the motherboard, or whether part
is accessible only through the bus.
     An alternate explanation is that 16 megahertz machines tend to be older
designs than 20 megahertz machines, and there may have been some subtle changes
in motherboard technology in the last couple of years which affect the relative
speeds of standard and enhanced modes.
    Once again, we are talking about computational speed in situations where
disks are not being accessed - disk caches and swapfiles are not involved.
--
Bruce Dunn   Vancouver, Canada    a752@mindlink.UUCP