From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: PS: A mysterious event
Date:	14 Aug 2000 12:45:40 GMT
Organization:	Aachen University of Technology (RWTH)
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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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