Fan speed control
Related articles
Fancontrol, part of lm_sensors, can be used to control the speed and sound of CPU/case fans. This article covers configuration/setup of the utility.
For some Dell laptops, an alternative is i8kutils.
Contents
Sensor driver
Support for newer motherboards may not yet be in the Linux kernel. Check the official lm-sensors devices table to see if experimental drivers are available for such motherboards.
It is recommended not to use lm_sensors.service
to load the needed modules for fancontrol. Instead, manually place them in /etc/modules-load.d/load_these.conf
since the order in which these modules are loaded dictate the order in which the needed symlinks for hwmon get created. In other words, using the lm_sensors.service
causes inconsistencies boot-to-boot which will render the configuration file for fan control worthless for a consistency point of view. To avoid this problem:
In /etc/conf.d/lm_sensors
you find the modules. If not there, run as root sensors-detect
accepting the defaults. In the modules-load.d
file place one module name per line. Specifying them like this will create a reproducible order. Another alternative is to use absolute device names in the configuration file.[1]
lm-sensors
Set up lm_sensors.
$ sensors
coretemp-isa-0000 Adapter: ISA adapter Core 0: +29.0°C (high = +76.0°C, crit = +100.0°C) [...] it8718-isa-0290 Adapter: ISA adapter Vcc: +1.14 V (min = +0.00 V, max = +4.08 V) VTT: +2.08 V (min = +0.00 V, max = +4.08 V) +3.3V: +3.33 V (min = +0.00 V, max = +4.08 V) NB Vcore: +0.03 V (min = +0.00 V, max = +4.08 V) VDRAM: +2.13 V (min = +0.00 V, max = +4.08 V) fan1: 690 RPM (min = 10 RPM) temp1: +37.5°C (low = +129.5°C, high = +129.5°C) sensor = thermistor temp2: +25.0°C (low = +127.0°C, high = +127.0°C) sensor = thermal diode
If the output does not display an RPM value for the CPU fan, one may need to increase the fan divisor. If fan speed is shown and higher than 0, skip the next step.
Increasing fan_div
The first line of the sensors output is the chipset used by the motherboard for readings of temperatures and voltages.
Create a file in /etc/sensors.d/
:
/etc/sensors.d/fan-speed-control.conf
chip "coretemp-isa-*" set fanX_div 4
Replacing coretemp-isa- with name of the chipset and X with the number of the CPU fan to change.
Save the file, and run as root:
# sensors -s
which will reload the configuration files.
Run sensors
again, and check if there is an RPM readout. If not, increase the divisor to 8, 16, or 32. YMMV!
Configuration
Once sensors is properly configured, run pwmconfig
to test and configure speed control. Follow the instructions in pwmconfig
to set up basic speeds. The default configuration options should create a new file, /etc/fancontrol
.
Tweaking
Users wishing more more control may need to tweak the generated configuration. Here is a sample configuration file:
INTERVAL=10 DEVPATH=hwmon0=devices/platform/coretemp.0 hwmon2=devices/platform/w83627ehf.656 DEVNAME=hwmon0=coretemp hwmon2=w83627dhg FCTEMPS=hwmon0/device/pwm1=hwmon0/device/temp1_input FCFANS= hwmon0/device/pwm1=hwmon0/device/fan1_input MINTEMP=hwmon0/device/pwm1=20 MAXTEMP=hwmon0/device/pwm1=55 MINSTART=hwmon0/device/pwm1=150 MINSTOP=hwmon0/device/pwm1=105
-
INTERVAL
: how often the daemon should poll CPU temps and adjust fan speeds. INTERVAL is in seconds.
The rest of the configuration file is split into (at least) two values per configuration option. Each configuration option first points to a PWM device which is written to which sets the fan speed. The second "field" is the actual value to set. This allows monitoring and controlling multiple fans and temperatures.
-
FCTEMPS
: The temperature input device to read for CPU temperature. The above example corresponds to/sys/class/hwmon/hwmon0/device/temp1_input
. -
FCFANS
: The current fan speed, which can be read (like the temperature) in/sys/class/hwmon/hwmon0/device/fan1_input
-
MINTEMP
: The temperature (°C) at which to SHUT OFF the CPU fan. Efficient CPUs often will not need a fan while idling. Be sure to set this to a temperature that you know is safe. Setting this to 0 is not recommended and may ruin your hardware! -
MAXTEMP
: The temperature (°C) at which to spin the fan at its MAXIMUM speed. This should be probably be set to perhaps 10 or 20 degrees (°C) below your CPU's critical/shutdown temperature. Setting it closer to MINTEMP will result in higher fan speeds overall. -
MINSTOP
: The PWM value at which your fan stops spinning. Each fan is a little different. Power tweakers canecho
different values (between 0 and 255) to/sys/class/hwmon/hwmon0/device/pwm1
and then watch the CPU fan. When the CPU fan stops, use this value. -
MINSTART
: The PWM value at which your fan starts to spin again. This is often a higher value than MINSTOP as more voltage is required to overcome inertia.
There are also two settings fancontrol needs to verify the configuration file is still up to date. The lines start with the setting name and a equality sign, followed by groups of hwmon-class-device=setting, seperated by spaces. You need to specify each setting for each hwmon class device you use anywhere in the config, or fancontrol will not work.
-
DEVPATH
: Sets the physical device. You can determine this by executing the command
readlink -f /sys/class/hwmon/hwmon-device/device | sed -e 's/^\/sys\///'
-
DEVNAME
: Sets the name of the device. Try:
$ sed -e 's/[[:space:]=]/_/g' /sys/class/hwmon/hwmon-device/device/name
fancontrol
Try to run fancontrol:
# /usr/bin/fancontrol
A properly configured setup will not error out and will take control of system fans. Users should hear system fans slowing shortly after executing this command.
To make fancontrol start automatically on every boot, enable fancontrol.service
.
i8kutils
i8kutilsAUR provides an alternative method of controlling the fan speed on some Dell Inspiron and Latitude laptops. It makes use of the /proc/i8k
interface provided by the dell_smm_hwmon
driver (formerly i8k
). Results will vary depending on the exact model of laptop.
Dependencies
tcl must be installed in order to run i8kmon
as a background service (using the --daemon
option). To run the X11 desktop applet, tk is required as well.
Configuration
By default, i8kmon
only monitors the CPU temperature and fan speed passively. To enable its fan speed control, either run it with the --auto
option or enable the option permanently in /etc/i8kutils/i8kmon.conf
:
set config(auto) 1
The temperature points at which the fan changes speed can be adjusted in the same configuration file. Only three fans speeds are supported (high, low, and off). Look for a section similar to the following:
set config(0) {{0 0} -1 55 -1 55} set config(1) {{1 1} 45 75 45 75} set config(2) {{2 2} 65 128 65 128}
This example starts the fan at low speed when the CPU temperature reaches 55 °C, switching to high speed at 75 °C. The fan will switch back to low speed once the temperature drops to 65 °C, and turns off completely at 45 °C.
Disable BIOS fan speed control
It may be necessary to turn off control of the fan speed by the BIOS to prevent it from "fighting" with i8kmon
. On some laptops, this can be done using the smm
utility. This utility is extremely dangerous as it writes directly to an I/O port to invoke the processor's System Management Mode. Use it at your own risk.
smm
must be compiled and installed manually. On a 64-bit system, gcc-multilib is required. Locate the file smm.c
in the i8kutils
source and compile it:
$ gcc -m32 -o smm smm.c
To disable BIOS fan speed control, run (as root):
# ./smm 30a3
To enable it again:
# ./smm 31a3
Installation as a service
i8kmon
can be started automatically as a systemd service using a unit file similar to the following:
/etc/systemd/system/i8kmon.service
[Unit] Description=i8kmon [Service] #ExecStartPre=/usr/bin/smm 30a3 # uncomment to disable BIOS fan control #ExecStopPost=/usr/bin/smm 31a3 # ... and re-enable it afterwards ExecStart=/usr/bin/i8kmon -d Restart=always RestartSec=5 [Install] WantedBy=multi-user.target