Heatsinks and ambient air...

Robert G. Brown rgb at phy.duke.edu
Thu Jun 14 13:20:52 EDT 2001


Dear Listhumans,

The indomitable and generally technically correct Mark Hahn pointed out
that current high-end CPUs dissipate more like 70-80W on maximum load
(and will run up to 90-95C, amazingly enough).  E.g. -- the 1.4 GHz
Athlon is rated to burn 72W under maximum load (quite enough to make an
EZ-bake oven out of.;-)

This means that a high end heat sink will keep it down to 50-60C in 20C
ambient air, not 40C (which number presumed a dissipation more in the
40-60W range) and a cheap heat sink will keep it barely alive at about
90-95C.  This is probably why AMD requires a decent heat sink and have
nice pictures and specs of what they mean by "decent" in the technical
specs available on their website.

It also means that setting the thermostat for your system room down to
15C (60F) is not a bad idea, in case you don't already run it down
there.

rgb regrets the error.  rgb has been used to a 50W CPU being pretty durn
hot in the Intel/AMD family at least.  rgb is clearly behind the times
-- again.  rgb is irritated that lm-sensors cannot seem to find a
thermal sensor on his new 1.33 GHz Tbird systems which might have kept
him from making such an easily corrected error.

Please do not consider this an excuse to reconsider liquid cooling.
Please.  My penguin has on a vest filled with TNT and is fully prepared
to go on a suicide mission.

   rgb

-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu




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