Subject: Re: Good news, bad news
To: NetBSD/alpha Discussion List <port-alpha@NetBSD.ORG>
From: Jack Twilley <>
List: port-alpha
Date: 02/01/2002 13:58:03
>>>>> "Greg" == Greg A Woods <> writes:

Jack> So maybe my problem is related to something else.  I clipped the
Jack> thermistor, and that had no effect.  I took the Multia
Jack> completely out of the case, and balanced it on a non-conducting
Jack> surface.  It still doesn't last more than ten minutes compiling
Jack> before it hangs.  The heat sink is touchable with bare
Jack> fingertips for a few moments before hurting.  Ditto for the 623.
Jack> It is easily the hottest chip on that side of the motherboard.

Greg> You know you're not supposed to run the Multia motherboard
Greg> without a fan.  If the heatsink is too hot to hold then it's
Greg> possible the die itself is nearly over-temp.  IIRC 125C is the
Greg> maximum and beyond that you risk damage.  Ross is far more
Greg> familiar with these cooling parameters than I and will no doubt
Greg> correct me if I'm wrong....  :-)

The room itself has a bit of airflow that exceeds the wimpy fan.  This
was the only way I could access the 623 in a running configuration.

Greg> As for the 74LS623, well if you can't comfortably hold your hand
Greg> on the surface of the chip casing then it's probably getting
Greg> close to being a bit too hot (125C is the max temp for the 623
Greg> too).  Considering that it'll get a LOT hotter in next to the
Greg> bottom of the case with no air-flow, it's probably suffered
Greg> over-temp conditions several times.  The symptoms you describe
Greg> are very likely caused by a dying 74LS623.  I forget exactly
Greg> how, but it's pretty closely related to the memory access path.

Okay.  That's the first confirmation I've received that this chip may
really be the fault.

Greg> Replace it, and secure a square of copper foil (or aluminium) to
Greg> the new one's surface, with some thermally conductive grease
Greg> under it, so that it can radiate a bit more heat.  See the
Greg> NetBSD/alpha Multia FAQ.

I have read the FAQ, and the repair job is a little intimidating.
Hopefully I won't kill the motherboard with the soldering iron, or
perhaps I can find someone who will do it for me in return for half a
liter of home-brew mead.

Greg> -- Greg A. Woods

Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash