From:	"Charles Sandmann" <sandmann AT clio DOT rice DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	ANNOUNCE: CWSDPMI r4 large memory bug workaround
Date:	Sun, 9 May 1999 21:30:16
Organization:	Aspen Technology, Inc.
Lines:	31
Message-ID:	<3735fe68.sandmann@clio.rice.edu>
NNTP-Posting-Host:	dmcap2.aco.aspentech.com
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com

It has recently come to my attention that there are some bugs in 
CWSDPMI r4 when handling large amounts of physical and/or virtual
memory.  The purpose of this note is to warn users of these problems
and provide workarounds where possible.  An updated release r5 which
fixes these problems will be released when I get a chance.

1) More than 128Mb of physical memory will not work properly.  There
   is an internal problem with signed/unsigned integers which causes
   page numbers above the 128Mb mark to cause page fault failures.
   Note that more than 256Mb physical memory will be treated modulo
   256Mb memory (384Mb memory is treated as 128Mb).

   Workaround:  Configure the memory available for CWSDPMI to be 
   limited to 128Mb of memory on machines with more than 128Mb of 
   memory.  The memory available must be the lower addresses.

2) More than 255Mb of total virtual address space will not work 
   properly.  This is due to a short integer overflow/wrap problem on
   internal data structure allocation size.  Since the default CWSDPMI is
   configured with 128Mb of virtual addressing, trying to use more than
   about 120Mb of memory on a 128Mb physical memory machine will cause
   page fault failures.

   Workaround:  Use CWSPARAM to modify the Maximum number of 4K pages
   in the swap file to a smaller number (or disable paging completely).

If you have less than 128Mb of physical memory and use the standard
distribution, you should not notice either of these problems.  If you
have 128Mb or more of physical memory and are trying to use it with 
CWSDPMI (probably through HIMEM.SYS) or have used CWSPARAM to increase
the swap file size you may encounter these problems. 

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