[PLUG] Newly assembled machine overheating

Keith Lofstrom keithl at kl-ic.com
Sat Sep 23 03:17:46 UTC 2006


On Fri, Sep 22, 2006 at 03:49:51PM -0700, Richard C. Steffens wrote:
> I have an overheating processor chip (thank you chip and mother board 
> makers for adding temperature sensing and alarms) and need some ideas on 
> what might be causing the problem.
> 
> I've just assembled a machine:
...
> That worked fine, and I could see the CPU temperature and the fact that 
> the alarm was enabled so I'd know when to start worrying about the CPU 
> getting too hot.
> 
> It took a fairly long time to finally get around to booting, but 
> eventually the SuSE 10.1 install CD booted. I entered the FTP site and 
> waited another fairly long time for the process to begin. Just as it 
> did, the alarm went off. I aborted the installation and rebooted. The 
> processor chip temperature was 44deg C. I recall that the limit is 45, 
> so I shut down the machine.
...

If the processor is getting very hot, then the heat sink should be
getting quite hot, too.  If it is not, then there is something blocking
the heat flow to the heat sink, for example a plastic film that is
supposed to be removed to expose a thermally conductive soft plastic.
Or the heat sink isn't properly anchored.  Or you have the wrong kind
of heat sink for your processor.  Or the processor voltage is too high
(check the BIOS for voltages, compare that to the processor type you
have).  Or the motherboard is bad.  Or the processor is bad.  Or ...?

I had a similar overheating problem with my wife's Shuttle ATX.  It
turned out to be a failed fan control on the motherboard.  Fortunately,
there was a second socket for the fan, so I just moved the fan plug to
that second socket.  

Some motherboards have all sorts of controls over fan speed in the BIOS.
Record the current fan settings (so you can restore them), then set the
fans to "high speed all the time".  If they still move slowly, that is
one problem, if they move fast but the chip still gets hot, then it
is probably the heat sink interface, or something not working.

It is a pity that most motherboards don't measure processor CURRENT.
That would tell you if something was broken in the CPU or on your
motherboard.  Still, if the voltage is too LOW, it could indicate
a problem with overcurrent.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs



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