From owner-freebsd-hardware  Thu Aug 21 02:12:47 1997
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Date: Thu, 21 Aug 1997 03:11:05 -0600 (MDT)
From: Doug Russell <drussell@saturn-tech.com>
To: Mike Smith <mike@smith.net.au>
cc: pius@ienet.com, freebsd-hardware@FreeBSD.ORG, terryl@ienet.com,
        robert@ienet.com
Subject: Re: wdunwedge failed 
In-Reply-To: <199708210157.LAA00493@word.smith.net.au>
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On Thu, 21 Aug 1997, Mike Smith wrote:

> > It flickers. For example, a screen full of these "wdunwedge failed" error
> > messages appears for a second or two and then the screen completely blanks
> > out for a second. Then the error messages are visible again briefly, then
> > the screen goes blank, and so no. Sort of like someone quickly turning the
> > monitor on and off.
> 
> It's possibly (as Brett suggested) that some delays in the wd code are 
> magically synchronising with something in the display driver, but I'd 
...

I'd guess either the error messages are just scrolling fast, and end up
flickering, or, especially by the way he describes it, that the video
signal is actually interrupted.

It may not be the problem, but I would take a multimeter and check out the
+12 volt supply while the machine is in this failed state.  The hard drive
most likely uses the 12 volt for spindle motor, etc., and most VGA cards
use the +12 and -12 supplies for the RAMDAC.  If the 12 volt line is
really funky (might need a scope to see if it is fluctuating, poorly
filtered due to a dead filter capacitor or something, etc.), the power
supply is the suspect.

Method B, of course, is to swap in a known good supply, and see if the
problem happens again.  :)

You'd be surprised how many strange problems are caused by a flakey power
supply.  Don't ever buy one of those cheapo $30 mini-tower (or whatever)
case deals.  The power supply in a $30 case probably isn't too wonderful.
Getting better built cases is an added bonus, too.  :)

Later..,....						<Doug>