Difference between revisions of "Fan speed control"

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(updated a couple areas to better comply with the style guide; replaced some HTML with wiki markup; added Filename and Codeline formatting; added Warning template to the warning message at the top; removed some abbreviations & improved some grammar)
(fancontrol: added note about i8kutils and i8kmon not working on the Inspiron 1764)
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It should start up and you will probably hear your CPU fan spin down.
It should start up and you will probably hear your CPU fan spin down.
If fancontrol is working, you may want to start up {{Codeline|fancontrol}} at boot via {{Filename|/etc/[[rc.conf]]}}.
If fancontrol is working, you may want to start up {{ic|fancontrol}} at boot via {{ic|/etc/[[rc.conf]]}}.
''Most of this HOWTO is from the [[http://ubuntuforums.org/ Ubuntu forums]] and the [[http://ubuntuguide.org/ Ubuntu guide]].''
''Most of this HOWTO is from the [[http://ubuntuforums.org/ Ubuntu forums]] and the [[http://ubuntuguide.org/ Ubuntu guide]].''
{{Note|For Dell Latitude/Inspiron laptops, you may want to use {{Pkg|i8kutils}}/{{Pkg|i8kmon}}.}}
{{Note|For Dell Latitude/Inspiron laptops, you may want to use {{Pkg|i8kutils}}/{{Pkg|i8kmon}}. Note that these two packages do ''not'' work on the Inspiron 1764.}}
=== Simple Bash script to fine tune fan speed ===
=== Simple Bash script to fine tune fan speed ===

Revision as of 06:13, 5 December 2011

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Controlling the speed (and sound!) of your CPU fan is easy!

Warning: This may ruin your hardware! A CPU fan is needed to cool your CPU and in this HOWTO, your CPU fan will be turned off for a couple of seconds. If you are not comfortable with doing this, then do not do this!


First, you need to set up lm_sensors.

Once you have lm_sensors installed, you should have a read-out with Template:Codeline.

$ sensors
Adapter: ISA adapter
Core 0:      +29.0°C  (high = +76.0°C, crit = +100.0°C)  

Adapter: ISA adapter
Core 1:      +29.0°C  (high = +76.0°C, crit = +100.0°C)  

Adapter: ISA adapter
Core 2:      +31.0°C  (high = +76.0°C, crit = +100.0°C)  

Adapter: ISA adapter
Core 3:      +29.0°C  (high = +76.0°C, crit = +100.0°C)  

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 your output does not display an RPM value for your CPU fan, and you are positive it is running, you need to increase the fan divisor. If your 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 your motherboard uses to read the speeds, temperatures, and voltages.

Create your libsensors configuration file by copying the default libsensors' configuration file to Template:Filename

# cp /etc/sensors3.conf /etc/sensors.d/sensors.conf

Edit Template:Filename and look up your exact chipset. A few chipset names are similar, so make sure the one you are editing is yours. Add the line 'set fanX_div 4' near the start of your chipset config, replacing X with the number of CPU fans your system has.

Save the file, and run as root:

# sensors -s

which will reload the sensors.conf's set variables. Run sensors again and check if there is an RPM readout. If not, increase the divisor to 8, 16 or 32. YMMV!


Note: Advanced users may want to skip this section and write Template:Filename on their own, which also saves them from hearing all of the fans at full speed.

Once you have lm sensors properly configured, run Template:Codeline to test and configure speed control of your fans.

Follow the instructions in Template:Codeline to set up basic speeds.

The default configuration options should create a new file, Template:Filename.


Warning: Some of the steps outlined below describe how to tweak fan speeds. Before doing this be sure you have low CPU load and are comfortable playing around. If at any time during tweaking you notice the CPU temperature start to rise dramatically, do a Template:Codeline to spin up the fan all the way until things cool down. Basically, you should know what you are doing before altering the configuration file.
Note: On several systems, the included script may report errors as it trys to calibrate your fan to the PWM. You may safely ignore these errors. The problem is that the script does not wait long enough before ramping up or down the PWM.

If you want more control, you will probably need to tweak the generated configuration. Here is a sample configuration file:

DEVPATH=hwmon0=devices/platform/coretemp.0 hwmon2=devices/platform/w83627ehf.656
DEVNAME=hwmon0=coretemp hwmon2=w83627dhg
FCFANS= hwmon0/device/pwm1=hwmon0/device/fan1_input
  • 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 you to monitor and control multiple fans and temperatures (if your PC supports it).

  • FCTEMPS: The temperature input device to read for cpu temperature. The above example corresponds to Template:Codeline.
  • FCFANS: The current fan speed, which can be read (like the temperature) in Template:Codeline
  • 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 can Template:Codeline different values (between 0 and 255) to Template:Filename 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
cat /sys/class/hwmon/<hwmon-device>/device/name | sed -e 's/[[:space:]=]/_/g'


Try to run fancontrol:


It should start up and you will probably hear your CPU fan spin down.

If fancontrol is working, you may want to start up fancontrol at boot via /etc/rc.conf.

Most of this HOWTO is from the [Ubuntu forums] and the [Ubuntu guide].

Note: For Dell Latitude/Inspiron laptops, you may want to use i8kutils/i8kmon. Note that these two packages do not work on the Inspiron 1764.

Simple Bash script to fine tune fan speed

Run this as root if you would like to see how various pwm values translate into fan RPM. As you can see, this script assumes that you have fancontrol running and disables it for you, then re-enables it when you are finished.


# change the following lines to match your system

# do not edit below this line
echo "PWM,RPM" > $log

echo "This script will set your PWM to values from full power down to 0 decreasing in"
echo "approx 5 % steps and pausing 10 sec between steps to allow the fan RPM to catch"
echo "up to the new settings.  Data are logged to ${log}"
echo "which can be used to generate a graph or use as-is."

collectdata() {
array=( 255 242 230 217 204 191 178 165 152 139 126 113 100 87 74 48 22 0 )
for item in ${array[*]}
echo $item > $pwmcontrol
sleep 10s
rpm=`cat ${fanrpmread}`
echo $item,$rpm >> $log
echo "PWM: ${item} RPM: ${rpm}"

/etc/rc.d/fancontrol stop
echo "1" > ${pwmcontrol}_enable


echo "0" > ${pwmcontrol}_enable
/etc/rc.d/fancontrol start