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From: jhunter AT kendaco DOT telebyte DOT com (Joel Hunter)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: CLI asm instruction
Date: Fri, 04 Aug 1995 06:36:08 GMT
Organization: Telebyte North West Silverdale, Wa
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References: <DCyttJ DOT A0L AT jade DOT mv DOT net>
Nntp-Posting-Host: kendaco.telebyte.com
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Dj-Gateway: from newsgroup comp.os.msdos.djgpp

Kevin Baca <kbaca AT skygames DOT com> wrote:

[SNIP]
>This works great under plain DOS, but under Windows it's about 20%
>slower.  If I remove the CLI, the performance goes back up, but then 
>my buffer gets trashed.  Anyone have any idea why the CLI slows 
>performance under Windows?

  If I remember correctly, under DPMI executing the CLI instruction
causes an exception.  The exception handler then goes and calls DPMI
function 0900h which disables the virtual interrupt state (hey, the
interrupt flag is privelaged and not just any application can mess
with it.)
  If you know you are going to be running under DPMI, I think it will
be considerable faster executing DPMI function 0900 -- of course, a
good chunk of that %20 could be just that Windows is a resource hog.

--
jhunter AT kendaco DOT telebyte DOT com