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From: Charles Sandmann <sandmann AT clio DOT rice DOT edu>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Clarification [Re: RAM limits]
Date: Sun, 17 Mar 2002 16:08:39 CST
Organization: Rice University, Houston TX
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> Did you mean that CWSDPMI will be able to obtain about 500Mb out of
> 768Mb (in my case) in true DOS, or that things might crash if I have
> more that 500Mb of physical RAM?  I assume you meant the former, that I
> will only be able to use 500Mb and the rest will lie dormant.

In true DOS, CWSDPMI will allow you to allocate the 768Mb (plus whatever
max swap size you've configured).  But you can only hold around 500Mb
of page directories in memory at once - so random access to more than
500Mb of memory can go relatively slowly in r5.  Sequential speed isn't
too bad (especially with a disk cache to speed up paging).

A work in progress (test version) of r6 uses 4Mb pages to get around
these problems (tested with 2Gb physical memory).  So far there has been
little need for more than 500Mb active random access RAM under CWSDPMI,
and those that need it are happy with the test version.

> On those Windows switches:  do you have a link to some extra info,
> perchance, or should I just start searching?

I had 896Mb in my W98 box at one time.  My video card only needed a 16Mb
AGP window.  I had to add:

[vcache]
MaxFileCache=524288

to my system.ini (a new section).  There were others which people 
advocated for large memory that I did not find necessary (so I didn't
keep a record of them).  This box now runs Win2000 99% of the time so
doesn't get much Win98 usage.