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Do your laptop fans produce a lot of noise?

July 28, 2007

Tecra Someone hoped my laptop doesn’t make too much noise after I posted a photo of the Tecra logo on Flickr. The short answer is no, it doesn’t make too much noise. At 10cm from the fan output, I can measure 42dB when the fan is off and 52dB when it’s on.

Beside the fact that I don’t hear that noise when I have my headphones, it was not sufficient for me. I wrote small python and gnuplot scripts to collect and display temperature, fan status and load (.tar.gz file, 1.3ko). During those 2 hours, I checked my e-mails, read news on the web and wrote the OPML output in catrss (that’s why load averages increase at the end, when I’m debugging the software). Here are the results (click on an image to see a larger version):

Temperature and load graph
Graph of temperature and load on a Toshiba Tecra S1 for 2 hours after boot

Temperature and fan activity graph
Graph of temperature and fan activity on a Toshiba Tecra S1 for 2 hours after boot (see text for explanation on fan activity)

One strange thing is that the status of both fans (/proc/acpi/fan/FAN0/state and /proc/acpi/fan/FAN1/state) is always off. But, when you ask for the trip points (/proc/acpi/thermal_zone/THZN/trip_points), you see that FAN1 should be active above 45°C and FAN0 should be active above 104°C! Practically, after some observations, I realized that FAN1 is activated if the temperature is equal to or above 50°C and it doesn’t stop until temperature is equal to or below 45°C. That’s the behaviour displayed in green on the second chart.

From → Open Source, Projects

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