From:	"Charles Sandmann" <sandmann AT clio DOT rice DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: HELP: How to install interupt handler create TSR program!
Date:	Sun, 24 Jun 2001 21:49:49
Organization:	Aspen Technology, Inc.
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Message-ID:	<3b36607d.sandmann@clio.rice.edu>
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> You can start with the sample code in v2tk/djgpptsr.zip, available
> from the usual DJGPP sites, it shows how to do that.
> 
> Note that protected-mode TSRs need functions that are only available
> with DPMI 1.0 servers.  CWSDPMI does support those functions, but the
> DPMI server built into Windows does not.  So if you want your TSRs to
> work on anything but plain DOS, you are probably out of luck.

Actually the TSR example doesn't use any of the DPMI 1.0 functions (and
CWSDPMI doesn't support any of the 1.0 DPMI stay resident functions).
What it does is to TSR the DJGPP stub executable, which then forces 
CWSDPMI to stay resident (since it never sees a DPMI exit call, so it
just thinks all remaining DPMI usages are nested.

This has some disadvantages, like:
  the 50-70Kb which CWSDPMI requires
  any PM horrible exception can't be cleared by unloading CWSDPMI

I remember the TSR example working on at least one other DPMI, but I can't
remember now which one it was.  I wasn't sure it would be a useful example,
but you never know what clever people will do with an example :-)

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