Subject: Re: Good news, bad news
To: Jack Twilley <jmt@twilley.org>
From: Greg A. Woods <woods@weird.com>
List: port-alpha
Date: 02/01/2002 15:50:36
[ On Thursday, January 31, 2002 at 23:01:36 (-0800), Jack Twilley wrote: ]
> Subject: Re: Good news, bad news
>
> So maybe my problem is related to something else.  I clipped the
> thermistor, and that had no effect.  I took the Multia completely out
> of the case, and balanced it on a non-conducting surface.  It still
> doesn't last more than ten minutes compiling before it hangs.  The
> heat sink is touchable with bare fingertips for a few moments before
> hurting.  Ditto for the 623.  It is easily the hottest chip on that
> side of the motherboard.

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

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

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

-- 
								Greg A. Woods

+1 416 218-0098;  <gwoods@acm.org>;  <g.a.woods@ieee.org>;  <woods@robohack.ca>
Planix, Inc. <woods@planix.com>; VE3TCP; Secrets of the Weird <woods@weird.com>