| 1 | .TH FANCONTROL 8 "January 2009" "lm-sensors 3" |
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| 2 | .SH NAME |
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| 3 | fancontrol \- automated software based fan speed regulation |
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| 4 | |
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| 5 | .SH SYNOPSIS |
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| 6 | .B fancontrol |
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| 7 | .I [configfile] |
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| 8 | |
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| 9 | .SH DESCRIPTION |
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| 10 | \fBfancontrol\fP is a shell script for use with lm_sensors. It reads its |
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| 11 | configuration from a file, then calculates fan speeds from temperatures and |
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| 12 | sets the corresponding PWM outputs to the computed values. |
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| 13 | |
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| 14 | .SH WARNING |
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| 15 | Please be careful when using the fan control features of your mainboard, in |
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| 16 | addition to the risk of burning your CPU, at higher temperatures there will be |
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| 17 | a higher wearout of your other hardware components, too. So if you plan to use |
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| 18 | these components in 50 years, \fBmaybe\fP you shouldn't use fancontrol |
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| 19 | at all. Also please keep in mind most fans aren't designed to be |
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| 20 | powered by a PWMed voltage. |
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| 21 | |
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| 22 | In practice it doesn't seem to be a major issue, the fans will get slightly |
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| 23 | warmer, just be sure to have a temperature alarm and/or shutdown call, in case |
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| 24 | some fan fails, because you probably won't hear it anymore ;) |
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| 25 | |
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| 26 | .SH CONFIGURATION |
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| 27 | For easy configuration, there's a script |
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| 28 | named \fBpwmconfig\fP(8) which lets you interactively write your |
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| 29 | configuration file for \fBfancontrol\fP. Alternatively you can write this |
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| 30 | file yourself using the information from this manpage. |
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| 31 | |
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| 32 | Since most of you are going to use \fBpwmconfig\fP(8) script, the config |
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| 33 | file syntax will be discussed last. First I'm going to describe the various |
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| 34 | variables available for changing \fBfancontrol\fP's behaviour: |
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| 35 | |
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| 36 | .TP |
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| 37 | .B INTERVAL |
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| 38 | This variable defines at which interval in seconds the main loop of |
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| 39 | \fBfancontrol\fP will be executed |
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| 40 | .TP |
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| 41 | .B FCTEMPS |
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| 42 | Maps PWM outputs to temperature sensors so \fBfancontrol\fP knows which |
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| 43 | temperature sensors should be used for calculation of new values for |
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| 44 | the corresponding PWM outputs. |
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| 45 | .TP |
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| 46 | .B FCFANS |
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| 47 | FCFANS records the association between a PWM and a fan. |
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| 48 | Then \fBfancontrol\fP can check the fan speed and restart it if it |
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| 49 | stops unexpectedly. |
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| 50 | .TP |
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| 51 | .B MINTEMP |
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| 52 | The temperature below which the fan gets switched to minimum speed. |
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| 53 | .TP |
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| 54 | .B MAXTEMP |
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| 55 | The temperature over which the fan gets switched to maximum speed. |
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| 56 | .TP |
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| 57 | .B MINSTART |
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| 58 | Sets the minimum speed at which the fan begins spinning. You should |
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| 59 | use a safe value to be sure it works, even when the fan gets old. |
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| 60 | .TP |
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| 61 | .B MINSTOP |
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| 62 | The minimum speed at which the fan still spins. Use a safe value here, |
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| 63 | too. |
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| 64 | .TP |
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| 65 | .B MINPWM |
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| 66 | The PWM value to use when the temperature is below MINTEMP. |
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| 67 | Typically, this will be either 0 if it is OK for the fan to plain |
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| 68 | stop, or the same value as MINSTOP if you don't want the fan to |
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| 69 | ever stop. |
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| 70 | If this value isn't defined, it defaults to 0 (stopped fan). |
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| 71 | .TP |
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| 72 | .B MAXPWM |
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| 73 | The PWM value to use when the temperature is over MAXTEMP. |
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| 74 | If this value isn't defined, it defaults to 255 (full speed). |
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| 75 | .PP |
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| 76 | The configuration file format is a bit strange: |
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| 77 | .IP |
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| 78 | .nf |
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| 79 | VARIABLE=chip/pwmdev=value chip/pwmdev2=value2 |
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| 80 | VARIABLE2=... |
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| 81 | .fi |
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| 82 | .PP |
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| 83 | Each variable has its own line. The variable name is followed by an equal sign |
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| 84 | and the device=value pairs. These consist of the path to the pwm output for |
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| 85 | which the value is valid, equal sign followed by the value and are separated |
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| 86 | by a blank. Path can be absolute or relative (from /sys/bus/i2c/devices or |
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| 87 | /sys/class/hwmon depending on the kernel version). Example: |
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| 88 | .IP |
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| 89 | MINTEMP=hwmon0/device/pwm1=40 hwmon0/device/pwm2=54 |
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| 90 | .PP |
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| 91 | You have to play with the temperature values a bit to get happy. For initial |
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| 92 | setup I recommend using the \fBpwmconfig\fP script. Small changes can be made by |
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| 93 | editing the config file directly following the rules above. |
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| 94 | |
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| 95 | .SH THE ALGORITHM |
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| 96 | |
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| 97 | \fBfancontrol\fP first reads its configuration, writes it to arrays and loops its |
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| 98 | main function. This function gets the temperatures and fanspeeds from |
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| 99 | kernel driver files and calculates new speeds depending on temperature |
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| 100 | changes, but only if the temp is between MINTEMP and MAXTEMP. After that, the |
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| 101 | new values are written to the PWM outputs. Currently the speed increases |
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| 102 | quadratically with rising temperature. This way you won't hear your fans most |
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| 103 | of the time at best. |
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| 104 | |
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| 105 | .SH SEE ALSO |
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| 106 | pwmconfig(8), sensors(1). |
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| 107 | |
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| 108 | .SH AUTHOR |
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| 109 | .PP |
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| 110 | Marius Reiner <marius.reiner@hdev.de> |
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