[Solved] Asus L1366 mobo, cpu fan speed control

Question

Hi, everyone,
I finally have this new core i7 system, to replace my old AMD athlonx2.  I have one question about the CPU fan speed control.
I remember that in my old system, the cpu fan speed control works out of box, no configuration is needed.
But when I install arch 64 on this new i7 system, the cpu fan is running at its maximum speed constantly while the CPU temperature is modestly low. I know there is a wiki teaching how to do it.
However, I am just curious why it doens't work out of box any more? Does CPU fan control work for you guys out of box normally? especially the new Core i7 cpu users?
Please let me know, really appreciated it.
Thanks a lot.
Update: the issue is solved, see my last post, the solution is blacklisting: asus_atk0110, instead use w83667hg.
Cheers.
Last edited by mark.altern (2009-10-01 08:18:18)

Answer 1

First off, it would be useful to know what the sensors-detect script actually reports.
Okay. How fan control works on Linux: First, navigate to /sys/class/hwmon
Each of these folders, i.e. hwmon0, stands for a sensors monitor / fan controller on your mainboard that may control one or several fans. Inside hwmonN, there should be a subfolder called device, which contains several interfaces if your BIOS allows software-side fan control. You can read them with cat and write to them with echo.
Examples:
pwm1_enable shows if OS-level fan control is enabled (1) or disabled and in BIOS control (0). Changing fan speed won't work if this is disabled. (i.e. cat /sys/class/hwmon0/device/pwm1_enable reports 0 -> disabled; you could enable it with echo 1 > /sys/class/hwmon0/device/pwm1_enable).
pwm1 allows to change fan speed. The values range from 0 (fan off) to 255 (full speed, 12V).
fan1_input shows the current RPM if a fan is connected. You can only read from this interface. Its useful to check all of these in the each of the hwmon folders to find out if there is actually a fan connected to the fan controller (they often have more ports than mainboard manufacturers use).
There might be a fan1_div, this is somehow related to how the kernel reads the RPM, I don't know how it works.
temp1_input interfaces can appeare too, if some of the chips have temperature sensors located somewhere. I *think* lm_sensors places the core temperatures it reads from CPU (the coretemp-isa-000X thingies) in one of the hwmon-folders too.
There might be interfaces for different fans in the same hwmon folder, i.e. pwm2_enable, pwm2, fan2_input, etc., all interfaces with the same index belong to the same physical fan connector, and all in the same hwmonN are managed by the same IC on your mainboard.
Warning: These interfaces, if they work, control the fans directly without any kind of security measure. If you shut some essential fan down, it will stay off until you reboot your CPU shuts down.
(If you see something likein0_alarm, in0_input, in0_max, etc. it's a voltage monitoring chip.)
If one of those interfaces can do something, OS-level fan control does work, if none of those folders contain a working pwm interface, fan control seems to be unavailable.
Sometimes there is an option in the BIOS to enable it, and for some BIOSs software-side fan control only works if dynamic fan control is disabled in the BIOS and fan speed is set to a static value - or vice versa.
I don't know what you are using to control fan speed, there are many applications that use these interfaces, i.e. GNOME or KDE power managers, so I'm not sure what is happening:
IF: Windows 7 enables OS-level fan control and sets it the RPM to those you observed and you have nothing that provides fan control in Arch and so fan control stays at BIOS-level, which might also read out a different sensor / the same sensor differently or it might be more conservative in setting fan speeds altogether;
OR: You have something that provides fan control installed in Arch and it reads out a the wrong value supplied by lm_sensors and thus sets a higher fan speed.
Anyway, possible solutions I can think of:
Find out if you have some kind of fan control software and what it does. For example, I use the fancontrol daemon, I can't help you if you use something else.
The wiki mentions how to assign a fan speed to a certain temperature sensors. You might assign it to a different one. For example, there are no sensor chips on the mainboard of my EEE (no temp1 etc.) so I assigned the fan speed to the temperature reported by the BIOS via ACPI (those are in /sys/class/thermal, also no "device" subfolder on EEEs):
FCTEMPS=/sys/class/hwmon/hwmon0/pwm1=/sys/class/thermal/thermal_zone0/temp
You could also change the MINTEMP/MAXTEMP values to one higher than those you actually want to compensate for the effect of lm_sensors reporting temperatures that are too high.
It is currently not possible for a mortal user to change the coretemps lm_sensors reads, see this post, last paragraph.
There is a configuration file, /etc/sensors3.conf, you can change sensor names and adjust offsets here, but only for the monitoring chips and their sensors that are on the mainboard.
Last edited by Malstrond (2009-08-19 19:34:22)