From 78ba196ad2a2f3894ab613f7ce08e5bb84ad3801 Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Sun, 3 Dec 2006 10:02:09 +0000 Subject: [PATCH] Update doc/fan-divisors. git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@4251 7894878c-1315-0410-8ee3-d5d059ff63e0 --- CHANGES | 1 + doc/fan-divisors | 28 +++++++++++----------------- 2 files changed, 12 insertions(+), 17 deletions(-) diff --git a/CHANGES b/CHANGES index ebd0239f..ab1b9237 100644 --- a/CHANGES +++ b/CHANGES @@ -3,6 +3,7 @@ lm_sensors CHANGES file SVN HEAD RPM: Obsolete, removed + File doc/fan-divisors: Update Library: Add support for the pc87247 driver (fans only) Probe for busses before chips Drop support for algorithm names diff --git a/doc/fan-divisors b/doc/fan-divisors index e1916bd0..4694cc14 100644 --- a/doc/fan-divisors +++ b/doc/fan-divisors @@ -4,9 +4,10 @@ Fan reading problems and solutions If you aren't getting the expected readings on your fans, try the following: -- Do you get a fan reading in the BIOS or in DOS? +- Do you get a fan reading in the BIOS or using a different OS? If not, you may not have a fan with a tachometer output. - Look and see. Fans with tachometer outputs have THREE wires. + Look and see. Fans with tachometer outputs have at least 3 wires. + Fans with only 2 wires cannot, in general, report their speed. - Try experimenting with the fan divisor settings: @@ -25,7 +26,6 @@ Fan Divisor Minimum RPM Maximum RPM 64 83 21093 "" 128 41 10546 "" - Pick a divisor so that the nominal RPM is about 50% above the minimum. This is a good compromise between margin and accuracy. Note that most chips only support @@ -46,13 +46,9 @@ accuracy. How to change fan divisors -------------------------- - Method 1: "echo x y z > /proc/sys/dev/sensors/...../fan_div" - where 'x y z' are the fan divisors for the three fans and '...' - is the sensor in question. - - Method 2: Put an entry "set fanx_div y" in the appropriate section - of /etc/sensors.conf and rerun 'sensors -s'. - (x is the number of the fan 1-3 and y is the divisor). +Put an entry "set fanN_div X" in the appropriate section of +/etc/sensors.conf and run 'sensors -s' +(N is the number of the fan, and X is the divisor you want). Further details @@ -69,7 +65,7 @@ The term 'fan divisor' is a misnomer because it doesn't divide the fan signal, it divides the 22.5 kHz clock. Thus you _increase_ the divisor if you have a slow fan. -The drivers account for the 'fan divisor' in its calculation +The drivers account for the 'fan divisor' in their calculation of RPM. So changing the fan divisor will NOT change the nominal RPM reading, it will only affect the minimum and maximum readings and the accuracy of the readings. @@ -86,18 +82,16 @@ fans do not approach 1,000,000 RPM ! Fan readings 2X too high ------------------------ -This is caused by a fan clock which is actually half the expected -22.5 kHz, or by a fan which outputs twice as many pulses per revolution -as expected. +This is rare, but can happen. This is typically caused by a fan which +outputs 4 pulses by revolution, instead of the standard 2. As we learned above, you can _not_ fix this by changing the fan divisor. You must add entries into the appropriate section of /etc/sensors.conf: - compute fan1 @/2, 2*@ - compute fan2 @/2, 2*@ - compute fan3 @/2, 2*@ + compute fanN @/2, 2*@ +(N is the number of the fan)