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fancontrol - automated software based fan speed regulation |
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Introduction |
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fancontrol is a shellscript for use with lm_sensors. It reads its |
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configuration from a file, then calculates fan speeds from temperatures and |
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sets the corresponding pwm outputs to the computed values. It is included in |
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lm_sensors since 2.8.0, the latest version is always available through SVN or |
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at http://www.hdev.de/fancontrol/ For easy configuration, there's a script |
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named pwmconfig which lets you interactively write your configuration file for |
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fancontrol. Alternatively you can write this file yourself using the |
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information from the configuration section of this document. |
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Please be careful when using the fan control features of your mainboard, in |
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addition to the risk of burning your CPU, at higher temperatures there will be |
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a higher wearout of your other hardware components, too. So if you plan to use |
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these components in 50 years, _maybe_ you shouldn't use fancontrol/your |
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hardware at all. Also please keep in mind most fans aren't designed to be |
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powered by a PWMed voltage, for more detailed information on this I recommend |
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this appnote: http://www.maxim-ic.com/appnotes.cfm/appnote_number/707 |
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In practice it doesn't seem to be a major issue, the fans will get slightly |
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warmer, just be sure to have a temperature alarm and/or shutdown call, in case |
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some fan fails, because you probably won't hear it anymore ;) |
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Configuration |
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Since most of you are going to use the prog/pwm/pwmconfig script, the config |
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file syntax will be discussed last. First I'm going to describe the various |
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variables available for changing fancontrol's behaviour: |
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INTERVAL |
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This variable defines at which interval in seconds the main loop of |
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fancontrol will be executed |
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FCTEMPS |
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Maps pwm outputs to temperature sensors so fancontrol know which |
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temperature sensors should be used for calculation of new values for |
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the corresponding pwm outputs. |
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FCFANS |
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FCFANS records the association between a pwm and a fan. |
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Then fancontrol can check the fan speed and restart it if it |
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stops unexpectedly. |
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MINTEMP |
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The temperature at which the fan gets switched off completely. |
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MAXTEMP |
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The temperature at which the fan gets switched to full speed. |
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MINSTART |
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Sets the minimum speed at which the fan begins spinning. You should |
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use a safe value to be sure it works, even when the fan gets old. |
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MINSTOP |
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The minimum speed at which the fan still spins. Use a save value here, |
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too. |
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If you set up your configuration by hand, be sure to include ALL variables and |
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use valid values, there's no error handling yet! The file format is a bit |
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strange: |
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VARIABLE=chip/pwmdev=value chip/pwmdev2=value2 [...] VARIABLE2=[...] |
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Each variable has its own line. The variable name is followed by an equal sign |
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and the device=value pairs. These consist of the relative path to the pwm |
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output (from /proc/sys/dev/sensors/) for which the value is valid, equal sign |
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followed by the value and are seperated by a blank. |
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Example: |
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MINTEMP=w83627hf-isa-0290/pwm2=40 w83627hf-isa-0290/pwm1=54 |
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You have to play with the temperature values a bit to get happy. For initial |
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setup I recommend using the pwmconfig script. Small changes can be made by |
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editing the config file directly following the rules above. |
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The algorithm |
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fancontrol first reads its configuration, writes it to arrays and loops its |
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main function. This function gets the temperatures and fanspeeds from |
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lm_sensors proc files and calculates new speeds depending on temperature |
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changes, but only if the temp is between MINTEMP and MAXTEMP. After that, the |
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new values are written to the pwm outputs. Currently the speed increases |
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quadratically with rising temperature. This way you won't hear your fans most |
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of the time at best. |
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Planned features |
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rc-scripts for some gnu/linux-distributions |
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smoother regulation (temp interpolation) |
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other curve styles (linear, exponential) |
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gui for configuration |
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If you have other wishes or want to contribute something, please let me know: |
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marius.reiner${AT}hdev.de |
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