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From:	"Charles Sandmann" <sandmann AT clio DOT rice DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: problem with 8254 (Timer)
Date:	Mon, 7 Jan 2002 17:17:37
Organization:	Aspen Technology, Inc.
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> In my old PC this program works correctly while in my Celeron 500Mz it does
> not work in DOS (real mode + CWSDPMI). It miss 350us every a lot, without
> regularity. Seems like an interrupt is executed but it is impossible because
> i have disabled them whith a CLI istruction. This problem can be caused 
> from NMI or from the CWSDPMI ???? Help me!

CWSDPMI doesn't issue any periodic interrupts (it's quite happy being out
of the way and turned off if you don't need it).  If you have issued a CLI
(and not done any operations which might have enabled interrupts - double
check this) then I suspect it's some NMI from your hardware.  You could
try installing a PM NMI handler which just does a IRET and see if that
helps; or try using the ring 0 version with an IRET (or PMODE 1.3).  If
an NMI happens it would be passed to real mode, and all of that could be
quite slow.

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