Cooling experts out there, some help please

alvin at alvin at
Tue May 8 20:53:05 PDT 2001

hi mark

heatsink compound makes a big difference too

and airflow or lack there of makes the biggest difference
in cpu temp....

I'd add i2c to one of the systems and start a cpu
temperature tests...over several days/weeks...
	- an idle cpu will give you "ambient cpu temperature"

it cpu temp is running hotter than spec...
you'd better add more fans to cool the systems...

every 10 degrees of heat in the cpu degrades the life
of the cpu by around 1/2 or something like that...

have fun
alvin ... 500Gb Raid5 in 1U ..

On Tue, 8 May 2001, Mark Hahn wrote:

> > What I am interested in a chart that define maximum
> > internal die temp / Die surface temp / Heat sink temp
> > for intel processors.
> well, if you look at a PIII datasheet, it indicates the max
> Tjunction is around 80C (lower for higher clocks, interestingly),
> fan intake are <= 45C.  I'd guess that the Tjunction-offset
> (diff between Tj and the internal diode reading) is a 
> conservative approximation of the deltaT between inner and 
> outer surface.  it's given as 4C.  so at the working surface
> of the heatsink, you need to be at, say, 76C.
> HS's seem to be characterized by vendors in thermal resistance, 
> deltaT per watt.  so a random Thermaltake unit lists .64C/W,
> which given, say, 24W for a PIII/733, means -16C cooler ambient,
> or a max of 60C in the case.
> as another example, P4/1700 specs say 64W thermal design power
> max Tcase 76C, Tambient 30C or so.  oddly, it also says 
> 50.2W of 1.7V power (85W, not 76!)
> > The chart could also specify different heatsink
> > material types CU,Al...
> design makes at least as much difference as material.
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