I have an overheating issue on my netbook (ASUS EeePC 1015PW), which I'm trying to troubleshoot. Using lm-sensors while overheating gave me this output :
acpitz-virtual-0 Adapter: Virtual device temp1: +86.0°C (crit = +100.0°C) eeepc-isa-0000 Adapter: ISA adapter fan1: 4089 RPM coretemp-isa-0000 Adapter: ISA adapter Core 0: +82.0°C (crit = +100.0°C) Core 1: +80.0°C (crit = +100.0°C)
But I couldn't hear the fan, even though the sensor claims it's spinning. So I enabled manual pwm controling and set the fan to full speed, and after a few minutes I got this output :
acpitz-virtual-0 Adapter: Virtual device temp1: +65.0°C (crit = +100.0°C) eeepc-isa-0000 Adapter: ISA adapter fan1: 4016 RPM coretemp-isa-0000 Adapter: ISA adapter Core 0: +62.0°C (crit = +100.0°C) Core 1: +58.0°C (crit = +100.0°C)
And this time I could hear the fan spinning. So there's quite obviously an issue with either fan control or fan monitoring. Hence the question : what kind of physical information does the fan sensor really report?
Why I'm pretty sure the man I'm controlling is the one I'm monitoring :
*** root # cd /sys/class/hwmon/hwmon2 *** hwmon2 # ls device fan1_input name power pwm1 pwm1_enable subsystem uevent *** hwmon2 # cat * cat: device: is a folder 4094 eeepc cat: power: is a folder 0 2 cat: subsystem: is a folder *** hwmon2 # echo 1 > pwm1_enable; echo 255 > pwm1 *** hwmon2 # cat * cat: device: is a folder 4016 eeepc cat: power: is a folder 255 1 cat: subsystem: is a folder
It seems that lm-sensors is reading the content of this fan1_input file, which is in the same folder as the pwm1 file I'm playing with, and they should be associated to the same device.
I have tried setting the fan to half speed
echo 125 > pwm1, the result was that the fan was still spinning though slower (logical) but the fan1_input contained 4094!
So I tried playing around... It turns out that at any speed below 242, the fan states that it spins at 4090-ish RPM (4094 each time I tried today), while above 243 it reports a speed of 4020-ish RPM (between 4015 and 4025).
And now I'm really puzzled... How can this be? Is it that the computer isn't reading the fan input on the same "scale" as the fan is providing it?
PS. I should have added that the computer is a small, hard-to-disassemble netbook, so I can't and don't want to try experiments like "block the fan and see what the sensor reports".