From:	"Greg Holdridge" <greg AT holdridge7 DOT freeserve DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: PS: A mysterious event
Date:	Tue, 15 Aug 2000 10:37:24 +0100
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Thanks a lot... I was aware word outs were unstable on some cards but I
didnt know the issue was still... an issue..

Greg

Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de> wrote in message
news:8n8plk$ere$1 AT nets3 DOT rz DOT RWTH-Aachen DOT DE...
> Greg Holdridge <greg AT holdridge7 DOT freeserve DOT co DOT uk> wrote:
> > Actually, sometimes a SIGSEGV occurs instead of power off on monitor-
this
> > highlights that the problem occurs during a lodsw loop:
> [...]
> > .SetCRTParmsLoop:
> >    lodsw           ;get the next CRT Index/Data pair
> >    out     dx,ax   ;set the next CRT Index/Data pair
> >    loop    .SetCRTParmsLoop
>
> If memory serves me well, this method of accessing IO ports is known
> to be dangerous, and known not to work, too. You're supposed to insert
> short pauses between succesive accesses to the CRT ports, esp. on
> modern CPUs. If you don't, you'll confuse the living daylight out of
> the CRT chip. Loss of VSync (--> blank screen) would be easily
> explained by that.
> --
> Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
> Even if all the snow were burnt, ashes would remain.

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