🚀 go-pugleaf

In article <73...@milton.u.washington.edu> wi...@milton.u.washington.edu (William Lewis) writes:
>In article <3061.2...@cc.helsinki.fi> mnyk...@cc.helsinki.fi writes:
>>The original PC could control the voltage going to the monitor, I've
>>heard, with similar results..
>
>   Actually, what could (can) be done was to reprogram the video
>controller chip to give an unexpected scan rate. This being before
>Multisync monitors =8) the flyback transformer would start generating
>lots of extra heat, and could eventually catch fire. (At least I think
>it was the flyback. The flyback is the generic folklore monitor component,
>anyway, after maybe the crt itself...) I think that at one time there was
>even a virus written to do this. However, because you had to *wait* for the
>heat to build up in the xformer, it took (I hear) about half an hour, with
>the picture meanwhile completely unreadable, to do any permament damage, 
>so this couldn't exactly be done subtly ...
>
>wi...@milton.acs.washington.edu       Seattle, Washington  | No sig under
>(William Lewis)   |  47 41' 15" N   122 42' 58" W  |||||||| construction

	Specifically, it was the 6845 chip found on Hercules Graphics
Cards, and (I must assume) the original MDA.  This was not, and never
will be, a problem with color cards such as the CGA and on up.  Sync
timing values can be altered by the user, causing potentially (see note
below) damaging frequencies.

	I quote from the Hercules Technical Reference Manual:  "Speed in
programming the 6845 is vital.  While the 6845 is being programmed,
undefined control frequencies are being sent to the monitor.  If this
condition is unduly prolonged, monitor damange may result."

	Back when I was in high school, I heard this cautionary tale.
However, I to this day have never heard a first-hand account of this
happening.  Have you had this happen to you?  If you have, why not
post about it?  I should note that I actually *work* for Hercules Technology
and I know the guy who designed the original HGS personally.  Perhaps
I should ask him, he might have done it himself... :-)

	Anyway, I suspect that modern monitors (especially multisyncs,
of course) are built with enough tolerance that the user could shut
down their monitor upon seeing a loss of sync LONG before any damage
could be done.

Dylan Rhodes
No .sig file, I think...