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From: dbell@cup.portal.com (David J Bell)
Newsgroups: rec.humor,comp.misc
Subject: Re: Looking for Computer Folklore
Message-ID: <15759@cup.portal.com>
Date: 13 Mar 89 02:09:58 GMT
References: <864@jato.Jpl.Nasa.Gov> <2047@tank.uchicago.edu> <36549@vax1.tcd.ie> <669@maths.tcd.ie>
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>>		I remember hearing that an early version of the Commodore
>>Pet would catch fire if certain addresses had certain contents. Something
>>about the clock being forced to run at too high a speed. (Can anyone confirm/
>>deny this?)

>had a _certain_ amount of control over the screen.  This meant that, if you
>REALLY knew what you were doing you could
>  (i) disable the refresh interrupt where the raster beam (the thing that
>  (ii) stop the beam in its place
>result: one VERY BRIGHT SPOT in the middle of the screen somewhere, which if
>        left will burn clean through the monitor, causing irreprable damage.
>
>This contradicted the first law of such machines: nothing you can type at the
>keyboard could do any PHYSICAL damage to the machine.  I wonder if anyone
>else has examples of this sort of behaviour?

Certainly! In fact, I inadvertently did this myself...

In an IBM PC/XT or clone, (AT, too, I'm sure) it is very easy to modify
the video controller VLSI device's parameter registers fom DEBUG or by
doing port outputs in BASIC. With some monitors, changing the horizontal
sync rate drastically can cause it to fry the horizontal output section
and high-voltage power supply. 

Dave