Mailinglist Archive: opensuse (1872 mails)

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[opensuse] Interesting CPU Fan Noise Observation
  • From: "David C. Rankin" <drankinatty@xxxxxxxxxxxxxxxxxx>
  • Date: Fri, 07 Nov 2008 01:31:48 -0600
  • Message-id: <4913EEE4.3040602@xxxxxxxxxxxxxxxxxx>

I have a relatively new 11.0 box with a phenom 9850 that is fairly
Recently I noticed the CPU fan noise quite a bit more than usual. I initially
thought that fan control was going on the fritz. I checked the temps and fan
speed with lm-sensors and confirmed fan RPM was pegged near max:

CPU Fan: 5338 RPM
CPU Temp: +33.0°C

Weird, the temp was only 33 degrees, not warm at all, not even a
concern. So I
waited a while and checked back. The noise had dropped a little, but not much.
It was still horrible:

CPU Fan: 5119 RPM
CPU Temp: +32.0°C

The case has 3 120mm 3-speed fans, all set on low. One in the bottom by
power supply, one on the back in the normal position, and one that blows out
the top through a screened housing.

On a whim, I decided to step up the 120mm fan on the back of the case
to the CPU. I set the fan control to medium where the 120mm fan is still quiet
and waited. In less than 5 seconds the CPU fan noise started dropping fast.
Within 30 seconds the CPU fan noise completely vanished. The box was for all
practical purposes near silent. I checked the temps again:

CPU Fan: 3282 RPM
CPU Temp: +31.0°C

That is absolutely incredible. Evidently the fan thermostat on the
stock AMD
cooler that comes with the processor has less than a 2 degree spread between
its 3200 RPM low noise state and its 5200 RPM annoying as hell state. Moreover,
the slight increase in the back-panel fan RPM from low to medium was just
enough to provide the slight additional amount of airflow needed to drop the
CPU temp by 1 degree and eliminate the noise. Just 1 degree made the difference
between an pleasant quite box and a costly additional expenditure for a water

That's it, ... I'm shooting the cats...

David C. Rankin, J.D., P.E.
Rankin Law Firm, PLLC
510 Ochiltree Street
Nacogdoches, Texas 75961
Telephone: (936) 715-9333
Facsimile: (936) 715-9339
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