Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!wugate!wuarchive!swbatl!texbell!vector!attctc!chasm
From: chasm@attctc.Dallas.TX.US (Charles Marslett)
Newsgroups: comp.os.minix
Subject: Re: Device drivers damaging HW
Summary: Power problems
Message-ID: <8804@attctc.Dallas.TX.US>
Date: 29 Jul 89 16:02:28 GMT
References: <13679@ea.ecn.purdue.edu> <4697@omepd.UUCP>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 37

In article <4697@omepd.UUCP>, pcm@iwarpj.intel.com (Phil C. Miller) writes:
> In article <13679@ea.ecn.purdue.edu> jel@ecn.purdue.edu (Jim Lumpp) writes:
> > ... How susceptible
> >is the IBM hardware to such damage?

> Some Hercules monochrome clone cards (not IBM, but used in IBM machines) get
> toasted inadvertantly if you're not careful.  The low-level mechanics of
> this are beyond my domain, but it's when you're trying to BLANK the screen
> that your problems start.  Hercules (and its clones) is implemented so that
> the DARKEST shade results from the HIGHEST voltage, BRIGHTEST shade from the
> LOWEST voltage.

This problem (as I understand it) is a result of using traces too thin or
narrow for the current consumed (especially to the RAM chips).  It occurred
only on Hercules CLONES [real Hercules cards never had the problem, to my
knowledge].  It cannot happen on multilayer cards with power and ground
planes, and is very unlikely to happen with newer cards because the RAMs
manufactured in the last three or four years pull a lot less current that
older ones.

Pardon me if the problem I am describing is not the one originally mentioned,
but if it is, It is again safe to mess things up, just turn off power if the
screen starts acting flakey -- you usually have 20 or 30 seconds for that.

> something so innocent as blanking the screen can toast your controller, your
> display, or both.
> 
> Sadder but wiser,
> 
> Phil Miller

Charles
===========================================================================
Charles Marslett
STB Systems, Inc.  <== Apply all standard disclaimers
Wordmark Systems   <== No disclaimers required -- that's just me
chasm@killer.dallas.tx.us <== soon to be attctc.dallas.tx.us I think