From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Swap memory available
Date: Fri, 16 Jan 1998 18:34:47 -0500
Organization: Two pounds of chaos and a pinch of salt.
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Daniel TAUPIN wrote:
> 
> > It's a runtime variable, determined by the amount of free physical
> > memory and free disk space on your computer.  By default, the cwsdpmi
> > DPMI host uses "c:\cwsdpmi.swp" for your swap file, so its value should
> 
> There is not cwsdpmi.swp in my computer!

Of course not.  It's generated on the fly and erased when your programs
exit.  However, if you want to see it in action, load a memory-intensive
application like Emacs in plain DOS and then search for 'cwsdpmi.swp' in
your root directory.  You can tell how much virtual memory you're using
by the size of the file (it's usually zero on my computer).  Under
Windows, you won't find any such file because cwsdpmi is not used.

> Yes, but does this explain the difference between what is said by
> GO32(v1) and GO32-V2?

Go32 (v1) does not use cwsdpmi; it has its own internal DOS extender
code and handles memory much differently than cwsdpmi or DJGPP v2 in
general.  On my machine, under Windows 95, go32 and go32-v2 give me the
following information:

[WIN] C:\djgpp\BIN>go32
go32 version 1.12.maint3 Copyright (C) 1994 DJ Delorie
Lowest version I can run is 1.08
go32.exe usage: go32 [-d {debugger}] [{program} [{options} . . . ]]
go32.exe build time was Sun Dec 18 16:36:42 1994
DPMI memory available: 35736 Kb
Swap space available: 2096832 Kb

[WIN] C:\djgpp\BIN>go32-v2
go32/v2 version 2.0 built Aug 12 1996 22:27:23
Usage: go32 coff-image [args]
Rename this to go32.exe only if you need a go32 that can run v2 binaries
as
 well as v1 binaries (old makefiles).  Put ahead of the old go32 in your
PATH
 but do not delete your old go32 - leave it in the PATH after this one.
Set GO32_V2_DEBUG=y in the environment to get verbose output.

DPMI memory available: 36111 Kb
DPMI swap space available: 29041 Kb

As you can see, go32 apparently records the total amount of hard drive
space you have remaining as virtual memory (as well as ignoring Windows'
DPMI host on the matter), while go32-v2 reports what the DPMI host
provides it (in this case, Windows is giving me 64 MB of virtual
memory).

FYI, my hd is formatted as FAT32, but applications not aware of FAT32
report a maximum size of 2 GB.

> > Oh, and don't worry about losing the use of that disk space.  cwsdpmi
> > only accesses swap space when it needs it; it leaves your hard drive
> > alone otherwise.  :-)
> >
> But the question is still: on which disk will cwsdpmi.swp be installed?
> C: or D:?
> And how can I decide it on D: rather than C:?

Go to your DJGPP bin directory and type 'cwsparam'.  It will allow you
to view and/or change the settings of cwsdpmi, including the name of the
swap file.  The default is, I believe, "c:\cwsdpmi.swp" but you can
change it to anything you like, including a nonexistent path.  (Doing
this will effectively disable virtual memory.)  You can press Enter to
leave the values unchanged.  cwsparam only changes the settings of the
'cwsdpmi.exe' in the current directory; if you have more than one copy
you'll need to update them all.

BTW, if you distribute programs using a modified cwsdpmi.exe, and the
swap file is set to a drive that does not exist on the user's computer,
virtual memory will not work.  You have been warned.

Please also note that under Windows 95, or any other environment that
provides DPMI services, cwsdpmi is NOT used.

hth

-- 
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|      John M. Aldrich       | "A committee is a life form with six |
|       aka Fighteer I       | or more legs and no brain."          |
|   mailto:fighteer AT cs DOT com   |                                      |
| http://www.cs.com/fighteer |                 - Lazarus Long       |
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