root/lm-sensors/tags/V2-10-2/doc/FAQ

Short Contents
**************

lm_sensors
1 PC and Sensor Overview
2 Sensor and Bus Basics
3 Installation and Management
4 Problems
5 How to Ask for Help
6 How to Contribute
Appendix A Revision History of This Document


Table of Contents
*****************

lm_sensors
1 PC and Sensor Overview
  1.1 What sensors are available on my PC?
  1.2 What can a sensor chip like the "LM78" do?
  1.3 Where do I find out more about any of these chips?
2 Sensor and Bus Basics
  2.1 How are these sensors read?
  2.2 What is the SMBus? And the I2C bus?
  2.3 I don't have an ISA bus!
  2.4 What sensors do processors have?
  2.5 How often are the sensor values updated?
  2.6 How are alarms triggered?
3 Installation and Management
  3.1 Why so many modules, and how do I cope with them?
  3.2 How do I know which chips I own?
    3.2.1 What chips are on motherboard XYZ?
    3.2.2 Do you support motherboard XYZ?
    3.2.3 Do you support chip XYZ?
    3.2.4 Anybody working on a driver for chip XYZ?
  3.3 Which modules should I insert?
  3.4 Do I need the configuration file `/etc/sensors.conf'?
    3.4.1 The labels for the voltage and temperature readings in `sensors' are incorrect!
    3.4.2 The min and max for the readings in `sensors' are incorrect!
    3.4.3 The min and max settings in `/etc/sensors.conf' didn't take effect!
    3.4.4 One sensor isn't hooked up on my board!
    3.4.5 I need help with `sensors.conf'!
    3.4.6 Do you have a database of `sensors.conf' entries for specific boards?
  3.5 What about the `No such file or directory' warnings when I compile?
  3.6 I get all kinds of weird compilation errors?
    3.6.1 `No rule to make target xxxx needed by xxxx' - how to fix?
  3.7 It still does not compile or patch!
  3.8 `make install' fails on Mandrake kernels
  3.9 I get unresolved symbols when I `modprobe' modules (Red Hat especially)
  3.10 I2C_DRIVERID_ADM1024 undefined (Red Hat especially)
4 Problems
  4.1 My fans report exactly half/double their values compared to the BIOS?
    4.1.1 Fans sometimes/always read 0!!
    4.1.2 I doubled the fan divisor and the fan still reads 7000!
  4.2 Why do my two LM75's report "-48 degrees"?
  4.3 Why do I have two Vcore readings, I have only one processor!
  4.4 How do those ALARMS work? The current value is within range but there is still an ALARM warning!
  4.5 My voltage readings seem to drift a bit. Is something wrong?
  4.6 Some measurements are way out of range. What happened?
    4.6.1 -5V and -12V readings are way out of range!
  4.7 What are VID lines? Why is the VID reading wrong?
  4.8 I read sensor values several times a second, but they are only updated only each second or so. Why?
  4.9 It sometimes seems to take almost a second before I see the sensor reading results. Why?
  4.10 Can I be alerted when an ALARM occurs?
  4.11 SMBus transactions on my PIIX4 simply don't work (timeouts happen).  Why?
  4.12 My BIOS reports a much higher CPU temperature than your modules!
  4.13 I try to read the raw `/proc' files, but the values are strange?!?
  4.14 How do I set new limits?
    4.14.1 I set new limits and it didn't work?
  4.15 Some sensors are doubly detected?
  4.16 I ran sensors-detect, but now I get very strange readings?!?
  4.17 Bad readings from particular chips
    4.17.1 Bad readings from the AS99127F!
    4.17.2 Bad readings from the VIA 686A!
    4.17.3 Bad readings from the MTP008!
    4.17.4 Bad temperature readings from the SIS5595!
    4.17.5 Bad readings from a w8378[12]d!
    4.17.6 Bus hangs on Ali 1543 on Asus P5A boards!
    4.17.7 Bad readings from LM75!
    4.17.8 Bad readings from LM78!
    4.17.9 Bad readings from LM80!
  4.18 How do I configure two chips (LM87) differently?
  4.19 Dmesg says `Upgrade BIOS'! I don't want to!
    4.19.1 Dmesg says `use force_addr=0xaddr'! What address do I use?
  4.20 Sensors says `Can't access procfs/sysfs file'
  4.21 Sensors says `No sensors found!'
  4.22 Sensors output is not correct!
  4.23 What is at I2C address XXX?
    4.23.1 What is at I2C address 0x69?
    4.23.2 What is at I2C addresses 0x50 - 0x57?
    4.23.3 What is at I2C addresses 0x30 - 0x37?
  4.24 Sensors-detect doesn't work at all
    4.24.1 Sensors-detect says "Couldn't open /proc/bus/i2c?!?"
    4.24.2 Sensors-detect says "Can't open /dev/i2c[-/]0"
    4.24.3 Sensors-detect doesn't find any sensors!
  4.25 Sensors says `Error: Line xxx: zzzzzzz'
  4.26 Sensors only gives the name, adapter, and algorithm for my chip
  4.27 Sensors says `ERROR: Can't get xxxxx data!'
  4.28 Sensors doesn't find any sensors, just eeproms.
  4.29 Inserting modules hangs my board
  4.30 Inserting modules slows down my board
  4.31 Problems on particular motherboards
    4.31.1 Asus P4B
    4.31.2 Tyan 2460, 2462
    4.31.3 Tyan 2466
    4.31.4 Tyan 2688
  4.32 Problems on particular systems
  4.33 Problems on 2.6 kernels
    4.33.1 i2c-viapro and via686a
    4.33.2 Where are my EEPROMs?
5 How to Ask for Help
  5.1 What to send us when asking for help
  5.2 What to do if a module won't insert?
  5.3 What to do if it inserts, but nothing happens?
  5.4 What to do if I read only bogus information?
  5.5 What to do if you have other problems?
  5.6 What if it just works like a charm?
  5.7 How do I update a ticket?
  5.8 How do I follow up on a ticket?
  5.9 Why did you decide not to support undocumented chips?
6 How to Contribute
  6.1 How to write a driver
  6.2 How to get SVN access
  6.3 How to donate hardware to the project
  6.4 How to join the project mailing lists
  6.5 How to access mailing list archives
  6.6 How to submit a patch
  6.7 How to REALLY help
  6.8 How to get release announcements
Appendix A Revision History of This Document


lm_sensors
**********

The lm_sensors package includes a collection of modules for general
SMBus access and hardware monitoring.  NOTE: this requires special
support which is not in standard 2.2-vintage kernels.

1 PC and Sensor Overview
************************

1.1 What sensors are available on my PC?
========================================

Most PC's built since late 1997 now come with a hardware health
monitoring chip. This chip may be accessed via the ISA bus or the
SMBus, depending on the motherboard.

   Some motherboard chipsets, notably the Via 686 and the SiS 5595,
contain hardware monitor functions.

   This FAQ frequently refers to the "LM78". This chip has been
obsoleted by National Semiconductor. Most motherboards today contain a
chip with similar functions.

1.2 What can a sensor chip like the "LM78" do?
==============================================

The LM78 is a chip made by National Semiconductor which can monitor 7
voltages (5 positive, 2 negative) from 0 to 4.08V.  The inputs are
usually in series with voltage dividers which lower the +/- 12V and +/-
5V supplies to measurable range.  Therefore, the readings for such
inputs need to be re-scaled appropriately by software.

   The LM78 also has 3 fan speed monitoring inputs, an internal
temperature sensor, a chassis intrusion sensor, and a couple maskable
interrupt inputs.  The LM78 can also relay the processor's (P6 or Pent
II) VID lines which are hardwired and used to indicate to the power
regulator (usually on the mainboard close to the processor socket/slot)
what voltage to supply to the processor.

   The LM78 can be interfaced to a system via the ISA bus and/or the
SMBus.

   Most other sensor chips have comparable functionality. Each supported
chip is documented in the `doc/chips' directory.

1.3 Where do I find out more about any of these chips?
======================================================

Most semiconductor companies have comprehensive documentation,
including complete datasheets, on their websites. Analog Devices,
Dallas Semiconductor, Maxim, and National Semiconductor have the widest
selection of sensor chips. Their websites are:

   * `http://www.analog.com'

   * `http://www.dalsemi.com'

   * `http://www.maxim-ic.com'

   * `http://www.national.com'

   Please see the file `http://www.lm-sensors.org/wiki/UsefulLinks' for
links to other companies' websites.

2 Sensor and Bus Basics
***********************

2.1 How are these sensors read?
===============================

Sensor chips reside on either the ISA bus, the SMBus, or both.  See the
file `doc/chips/SUMMARY' in our package for a list.

   To communicate with chips on the ISA bus, the software uses simple
I/O reads and writes.

   To communicate with chips on the SMBus, the software must use an
SMBus interface device, explained below.

2.2 What is the SMBus? And the I2C bus?
=======================================

The SMBus is the "System Management Bus".  More specifically, it is a
2-wire, low-speed serial communication bus used for basic health
monitoring and hardware management. It is a specific implementation of
the more general I2C (pronunciation: I-squared-C) bus. In fact, both
I2C devices and SMBus devices may be connected to the same (I2C) bus.

   The SMBus (or I2C bus) starts at the host controller, used for
starting transactions on the SMBus.  From the host interface, the
devices communicated with are the "slave" devices.  Each slave device
has a unique 7-bit address which the host uses to refer to that device.

   For each supported SMBus host, there is a separate kernel module
which implements the communication protocol with the host. Some SMBus
hosts really operate on the SMBus level; these hosts can not cope with
pure I2C devices. Other hosts are in fact I2C hosts: in this case, we
implement the SMBus protocol in terms of I2C operations. But these
hosts can also talk to pure I2C devices.

2.3 I don't have an ISA bus!
============================

We promise, you do, even if you don't have any old ISA slots.  The "ISA
Bus" exists in your computer even if you don't have ISA slots; it is
simply a memory-mapped area, 64KB in size (0x0000 - 0xFFFF) where many
"legacy" functions, such as keyboard and interrupt controllers, are
found. It isn't necessarily a separate physical bus.  See the file
`/proc/ioports' for a list of devices living on the "ISA Bus" in your
system. If you don't like the term "ISA Bus" think "I/O Space".

2.4 What sensors do processors have?
====================================

Most new processors contain a thermal diode on the die itself.  The
electical properties of all diodes and transistors vary slightly with
temperature. The thermal diode is exceptionally accurate because it is
directly on the die. Newer temperature sensor chips, like the Analog
Devices ADM1021 and clones, and the Winbond chips, have circuitry for
measuring the the electrical properties of an external diode and
converting this data to a temperature.  Any sensor chip listed in
`doc/chips/SUMMARY' in our package which has support for more than one
temperature supports external temperature sensing.

   Older motherboards and processors without this feature generally use
an LM75 placed close to the processor. This is much less accurate.

   The Pentium 2 'boxed' processor usually has an LM75 very close to the
base of the box. It can be read through the SMBus to report the
approximate temperature of the processor.  The processor also contains
an internal temperature sensor (of low accuracy) used as a fail-safe to
disable the processor in case it gets much too hot (usually around 130
degrees C).  And, the Pentium 2 also has a hard-wired signal (VID
lines) on it's SEC (single edge connector) which indicates what power
supply is required to operate the processor.

   The P6 (Pentium-Pro) may have an LM75 in or just under the socket.
P6's also have VID lines.

   Pentiums and Pentium w/ MMX do not have VID lines, and sometimes have
LM75's under the sockets (depends on the mainboard, and how 'modern' the
mainboard is).

   The P2 Xeon was the first Intel processor to include the SMBus
interface on the P2 Xeon SEC.

2.5 How often are the sensor values updated?
============================================

The LM78, and most other sensor chips like it, reads its sensors one by
one. A complete scanning sweep will take about 1.5 seconds. The LM78
stops readings sensors if you try to access it, so if you access it
very often (by reading sensor values; writing new limits is safe) it
will not find the time to update its sensor values at all! Fortunately,
the kernel module takes care not to do this, and only reads new values
each 1.5 seconds. If you read the values again, you will get the 'old'
values again.

2.6 How are alarms triggered?
=============================

It is possible to monitor each sensor and have an alarm go off if it
crosses some pre-determined limits.  There are two sorts of interrupts
which can be generated by sensor chips if this happens (it depends a
bit on the actual chip if both are supported; the LM80, for example,
has only IRQ interrupts): IRQ interrupts and SMI interrupts.  IRQ
stands for Interrupt Request and are the interrupt lines you can find
in `/proc/interrupts'.  SMI stands for System Management Interrupt, and
is a special interrupt which puts the processor in a secure environment
independent of any other things running.  SMI is currently not
supported by the Linux kernel.  IRQs are supported, of course.

   Even if no interrupt is generated, some bits in a status register
will be set until the register is read the next time. If the alarm
condition persists after that, the bits will be set on the next
scanning sweep, etc.

   Most drivers in our package do not support interrupts at this time.

3 Installation and Management
*****************************

3.1 Why so many modules, and how do I cope with them?
=====================================================

We tried to make this package as modular as possible. This makes it
easy to add new drivers, and unused drivers will take no precious kernel
space. On the other hand, it can be a bit confusing at first.

   Here are two simple guidelines:
   * Run `sensors-detect' and do what it tells you.

   * Always use `modprobe', not `insmod'.

   Further information is in `doc/modules'.

3.2 How do I know which chips I own?
====================================

We have an excellent program that scans all your hardware.  It is
called `sensors-detect' and is installed in `/usr/local/sbin' by `make
install'. Just execute this script, and it will tell you.

   Chip detection in the drivers is fairly good. That means that it is
usually harmless to insert more chip drivers than you need. However,
this can still lead to problems, so we do not recommend it.

   If sensors-detect didn't find any sensors, either you don't have
any, or the ones you have, we don't support. (Look at your motherboard
for candidates, then *note Help::)

3.2.1 What chips are on motherboard XYZ?
----------------------------------------

*!!!!!!!!! YES THIS IS THE MOST FREQUENT QUESTION WE GET !!!!!!!!!*

   We have no idea. Here is what you should do:
  1. Run sensors-detect.

   If that doesn't work:
  2. Look at your motherboard.

  3. Check the manufacturer's website or ask their support

  4. Check the Motherboard Monitor (http://mbm.livewiredev.com/)
     website and the "links"
     (http://www.lm-sensors.org/wiki/UsefulLinks) page on our website
     (http://www.lm-sensors.org) some good cross-references.

3.2.2 Do you support motherboard XYZ?
-------------------------------------

We don't support boards, we support chips. *Note What chips are on
motherboard XYZ: Section 3.2.1.

3.2.3 Do you support chip XYZ?
------------------------------

This we have good answers for.
   * Sorted by Manufacturer:   `README'

   * Sorted by Manufacturer:   `http://www.lm-sensors.org/wiki/Devices'

   * Sorted by Sensor Driver:  `doc/chips/SUMMARY'

3.2.4 Anybody working on a driver for chip XYZ?
-----------------------------------------------

Newest Driver Status: `http://www.lm-sensors.org/wiki/Devices'

3.3 Which modules should I insert?
==================================

`sensors-detect' will tell you. Take the `modprobe' lines it recommends
and paste them into the appropriate `/etc/rc.d/xxxx' file to be
executed at startup.

   You need one module for each sensor chip and bus adapter you own; if
there are sensor chips on the ISA bus, you also need `i2c-isa.o'.  for
each type of chip you own. That's all. On my computer, I could use the
following lines:
   * `modprobe i2c-isa'

   * `modprobe i2c-piix4'

   * `modprobe lm78'

   * `modprobe lm75'

   * `modprobe i2c-dev'

   * `sensors -s'

3.4 Do I need the configuration file `/etc/sensors.conf'?
=========================================================

Yes, for any applications that use `libsensors,' including the
`sensors' application included in our package.  It tells libsensors how
to translate the values the chip measures to real-world values. This is
especially important for voltage inputs. The default configuration file
should usually do the trick.  It is automatically installed as
`/etc/sensors.conf', but it will not overwrite any existing file with
that name.

3.4.1 The labels for the voltage and temperature readings in `sensors' are incorrect!
-------------------------------------------------------------------------------------

Every motherboard is different. You can customize the labels in the
file `/etc/sensors.conf'. That's why it exists!  The default labelling
(in `lib/chips.c' and `/etc/sensors.conf') is just a template.

3.4.2 The min and max for the readings in `sensors' are incorrect!
------------------------------------------------------------------

You can customize them in the file `/etc/sensors.conf'. See above.

3.4.3 The min and max settings in `/etc/sensors.conf' didn't take effect!
-------------------------------------------------------------------------

You forgot to run `sensors -s'. See above.

3.4.4 One sensor isn't hooked up on my board!
---------------------------------------------

Use an `ignore' line in `/etc/sensors.conf' so it isn't displayed in
`sensors'.

3.4.5 I need help with `sensors.conf'!
--------------------------------------

There is detailed help at the top of that file.

3.4.6 Do you have a database of `sensors.conf' entries for specific boards?
---------------------------------------------------------------------------

No. Good idea though. If you would like to set one up on your website
send us mail and we will set up a link to it.

3.5 What about the `No such file or directory' warnings when I compile?
=======================================================================

Don't worry about them. The dependency files (which tell which files
should be recompiled when certain files change) are created
dynamically. They are not distributed with the package. The `make'
program notices they are not there, and warns about that - and the
first thing it will do is generate them. So all is well.

3.6 I get all kinds of weird compilation errors?
================================================

Check that the correct i2c header files are used. Depending on how you
installed, they should be under either `/usr/local/include' or
`/usr/src/linux*/include'. Try to edit the `Makefile' for the other
setting.

3.6.1 `No rule to make target xxxx needed by xxxx' - how to fix?
----------------------------------------------------------------

   * *Note I get all kinds of weird compilation errors: Section 3.6,
     also try `make clean' in `lm_sensors'.

   * If that doesn't work, try `make clean' in `i2c'.

   * If that doesn't work, try `make clean' in the kernel.

   * Also make sure `/usr/include/linux' points to
     `/usr/src/linux/include/linux'.

3.7 It still does not compile or patch!
=======================================

Have you installed the matching version of the i2c package? Remember,
compilation is not enough, you also need to install it for the header
files to be found!

   If you want to patch the kernel, you will have to apply the i2c
patches first!

3.8 `make install' fails on Mandrake kernels
============================================

Mandrake uses a non-standard `version.h' file which confuses our
`Makefile'.  Edit our `Makefile' on the `MODDIR :=' line to hard-code
the module directory.

3.9 I get unresolved symbols when I `modprobe' modules (Red Hat especially)
===========================================================================

Example:
     *** Unresolved symbols in /lib/modules/2.4.5/kernel/drivers/i2c/i2c-i810.o
     i2c_bit_add_bus_R8c3bc60e
     i2c_bit_del_bus_R92b18f49

   You can also run `depmod -a -e' to see all unresolved symbols.

   These are module versioning problems. Generally you did not compile
against the kernel you are running. Sometimes the Red Hat source you
have is not for the kernel you are running.  You must compile our
package against the source for the kernel you are running with
something like `make LINUX=/usr/src/linux-2.4.14'.

   Try the following to be sure:

   * `nm --extern MODULE.o' Filter out the kernel symbols, like
     `kmalloc', `printk' etc. and note the number code behind them,
     like `printk_R1b7d4074'. If there is no numeric code after them,
     note this too.

   * `grep SYMBOL /proc/ksyms' Substitute SYMBOL by the basename of the
     symbols above, like `kmalloc', `printk' etc. Note the number code
     behind them, or the lack thereof.

   * Compare both sets of symbols. Are they the same? If so, the problem
     lies somewhere else. Are they different? If so, you have a module
     versioning problem.

3.10 I2C_DRIVERID_ADM1024 undefined (Red Hat especially)
========================================================

In some versions of Redhat, an RPM is included to provide i2c support.
However, this RPM does not place the header files in the kernel
directory structure.  When you update kernels, they may persist.  To
get rid of these obsolete header files, at a command prompt:

  1. `rpm -qa | grep i2c'

  2. Look for `kernel-i2c,' or a similar rpm in the output

  3. <as root> `rpm -ev kernel-i2c' (or the name of the similar package)
     If this complains about dependencies, you can try adding
     `--nodeps', but this *MAY* break something else.  Not likely, as
     you have upgraded kernels, and nothing should be using the old i2c
     stuff anymore anyway.  Just don't use it with abandon.

  4. Try (in the build directory of `lm_sensors)'
          `make clean'
          `make'

  5. _If_ you still have problems, you may have to replace the include
     paths in the `.c/.h' files with absolute paths to the header files.
     More of a workaround than a real fix, but at least you can get it
     to work.

4 Problems
**********

4.1 My fans report exactly half/double their values compared to the BIOS?
=========================================================================

The problem with much of the sensor data is that it is impossible to
properly interpret some of the readings without knowing what the
hardware configuration is.  Some fans report one 'tick' each rotation,
some report two 'ticks' each rotation. It is easy to resolve this
through the configuration file `/etc/sensors.conf':

     chip lm78-*             # Or whatever chip this relates to
     compute fan1 2*@,@/2    # This will double the fan1 reading
                             # -- or --
     compute fan1 @/2,2*@    # This will halve the fan1 reading

   See `doc/fan-divisors' in our package for further information.

4.1.1 Fans sometimes/always read 0!!
------------------------------------

You may not have a three-wire fan, which is required.

   You may need to increase the 'fan divisor'. See `doc/fan-divisors'
in our package for further information.

4.1.2 I doubled the fan divisor and the fan still reads 7000!
-------------------------------------------------------------

Believe it or not, doubling the 'fan divisor' will not halve the fan
reading. You have to add a compute line in `/etc/sensors.conf'.  *Note
My fans report exactly half/double their values compared to the BIOS:
Section 4.1, and see `doc/fan-divisors' in our package for further
information.

4.2 Why do my two LM75's report "-48 degrees"?
==============================================

For starters, those aren't LM75's.  Your mainboard actually has the
Winbond W83781D which emulates two LM75's, but many systems which use
the Winbond chip (such as the Asus P2B) don't have the thermo-resisters
connected to the chip resulting in these strange -48 degree readings.

   In upcoming versions, you will be able to disable non-interesting
readings.

4.3 Why do I have two Vcore readings, I have only one processor!
================================================================

The LM78 has seven voltage sensors. The default way of connecting them
is used in the configuration file. This includes a VCore2, even if you
do not have one. You can easily edit the configuration file to give it
another name, or make this reading disappear using an `ignore' line.

   Note that Vcore2 is often the same as Vcore on motherboards which
only support one processor. Another possibility is that Vcore2 is not
connected at all and will not have a valid reading at all.  A third
possibility, is that Vcore2 monitors something else, so you should not
be too surprised if the values are completely different.

4.4 How do those ALARMS work? The current value is within range but there is still an ALARM warning!
====================================================================================================

The ALARM indications in `sensors' are those reported by the sensor
chip itself. They are NOT calculated by `sensors'. `sensors' simply
reads the ALARM bits and reports them.

   An ALARM will go off when a minimum or maximum limit is crossed.
The ALARM is then latched - that is, it will stay there until the
chip's registers are next accessed - which will be the next time you
read these values, but not within (usually) 1.5 seconds since the last
update.

   Reading the registers clears the ALARMS, unless the current value is
still out of range.

   The purpose of this scheme is to tell you if there has been a
problem and report it to the user. Voltage or temperature spikes get
detected without having to read the sensor chip hundreds of times a
second. The implemetation details depend a bit on the kind of chip.
See the specific chip documentation in `doc/chips' and the chip
datasheet for more information.

4.5 My voltage readings seem to drift a bit. Is something wrong?
================================================================

No, probably not. If your motherboard heats up a bit, the sensed
voltages will drift a bit. If your power supply is loaded (because a
disk gets going, for example), the voltages may get a bit lower. Heavy
processor activity, in particular, dramatically increases core voltage
supply load which will often cause variation in the other supplies.  As
long as they stay within a sensible range (say 5% of the nominal value
for CPU core voltages, and 10% for other voltages), there is no reason
to worry.

4.6 Some measurements are way out of range. What happened?
==========================================================

Each module tries to set limits to sensible values on initialization,
but a module does not know how a chip is actually connected. This is
described in the configuration file, which is not read by kernel
modules.  So limits can be strange, if the chip is connected in a
non-standard way.

   Readings can also be strange; there are several reasons for this.
Temperature sensors, for example, can simply not be present, even though
the chip supports them. Also, it can be that the input is used in a
non-standard way. You can use the configuration file to describe how
this measurement should be interpreted; see the comments the example
file for more information.

4.6.1 -5V and -12V readings are way out of range!
-------------------------------------------------

It's very frequent that negative voltage lines are not wired because
motherboard manufacturers don't think they're worth monitoring (they
are mostly unused these days). You can just add `ignore inN' lines to
`/etc/sensors.conf' to hide them.

   Another possibility is that these lines are used to monitor different
voltages. Only the motherboard manufacturer can tell for sure. Taking a
look at what voltage values the BIOS displays may provide valuable
hints though.

4.7 What are VID lines? Why is the VID reading wrong?
=====================================================

These describe the core voltage for your processor. They are supported
for most processors, however they are not always correctly connected to
the sensor chip, so the readings may be invalid.  A reading of 0V,
+3.5V or +2.05V is especially suspect.  If this is the case, add a line
`ignore vid' to `/etc/sensors.conf', and change the min and max
settings for the Processor Core voltage (often in0_min and in0_max) in
that file so that they don't depend on vid.

   The CPU nominal voltage is computed from VID lines according to a
formula that depends on the CPU type. Most chips that report a VID
value can be configured to use either VRM 8.2 (for Pentium III) or VRM
9.0 (for Pentium 4 and Athlon). You chose which one you want through
`/etc/sensors.conf'.  See `doc/vid' for more information.

4.8 I read sensor values several times a second, but they are only updated only each second or so. Why?
=======================================================================================================

If we would read the registers more often, it would not find the time
to update them. So we only update our readings once each 1.5 seconds
(the actual delay is chip-specific; for some chips, it may not be needed
at all).

4.9 It sometimes seems to take almost a second before I see the sensor reading results. Why?
============================================================================================

ISA bus access is fast, but SMBus access is really slow. If you have a
lot of sensors, it just takes a lot of time to access them. Fortunately,
this has almost no impact on the system as a whole, as another job can
run while we are waiting for the transaction to finish.

4.10 Can I be alerted when an ALARM occurs?
===========================================

No, you can't; and it may well be never supported.

   Almost no mainboard we have encountered have actually connected the
IRQ-out pin of sensor chips. That means that we could enable IRQ
reporting, but nothing would happen. Also, even if a motherboard has it
connected, it is unclear what interrupt number would be triggered. And
IRQ lines are a scarce facility, which means that almost nobody would
be able to use it anyway.

   The SMI interrupt is only available on a few types of chips. It is
really a very obscure way to handle interrupts, and supporting it under
Linux might be quite hard to do.

   Your best bet would be to poll the alarm file with a user-land daemon
which alerts you if an alarm is raised. I am not aware of any program
which does the job, though you might want to examine one of the
graphical monitor programs under X, see
`http://www.lm-sensors.org/wiki/UsefulLinks' for addresses.

4.11 SMBus transactions on my PIIX4 simply don't work (timeouts happen).  Why?
==============================================================================

Some chips which mainboard makers connect to the SMBus are not SMBus
devices.  An example is the 91xx clock generator chips.  When read,
these devices can lock up the SMBus until the next hard reboot.  This
is because they have a similar serial interface (like the I2C), but
don't conform to Intel's SMBus standard.

   Why did they connect these devices to the SMBus if they aren't
compatible?  Good question! :')  Actually, these devices may support
being written to, but lock things up when they are read.

4.12 My BIOS reports a much higher CPU temperature than your modules!
=====================================================================

We display the actual temperature of the sensor. This may not be the
temperature you are interested in, though.  If a sensor should measure
the CPU temperature, it must be in thermal contact with it.  In
practice, it may be just somewhere nearby. Your BIOS may correct for
this (by adding, for example, thirty degrees to the measured
temperature).  The correction factor is regrettably different for each
mainboard, so we can not do this in the module itself. You can do it
through the configuration file, though:

     chip lm75-*-49                      # Or whatever chip this relates to
     label temp "Processor"
     compute temp @*1.2+13,(@-13)/1.2    # Or whatever formula

   However, the offset you are introducing might not be necessary. If
you tried to have Linux idle temperature and BIOS "idle" temperature
match, you may be misguided.  We have a Supermicro (370DLE) motherboard
and we know that its BIOS has a closed, almost undelayed while(1) loop
that keeps the CPU busy all the time. Linux reads 26 degrees idle, BIOS
reads 38 degrees. Linux at full load is in the 35-40 degrees range so
this makes sense.

4.13 I try to read the raw `/proc' files, but the values are strange?!?
=======================================================================

Remember, these values do not take the configuration file `compute'
lines in account. This is especially obvious for voltage readings
(usually called in? or vin?). Use a program linked to libsensors (like
the provided `sensors' program) instead.

4.14 How do I set new limits?
=============================

Change the limit values in `/etc/sensors.conf' and then run `sensors
-s'.

4.14.1 I set new limits and it didn't work?
-------------------------------------------

You forgot to run `sensors -s'. Put it in a `/etc/rc.d/...' file after
the modprobe lines to run at startup.

4.15 Some sensors are doubly detected?
======================================

Yes, this is still a problem. It is partially solved by alias detection
and confidence values in sensors-detect, but it is really tough.

   Double detections can be caused by two things: sensors can be
detected to both the ISA and the SMBus (and if you have loaded the
approprate adapter drivers, it will be detected on both), and some
chips simulate other chips (the Winbond W83781D simulates LM75 chips on
the SMBus, for example). Remove the offending adapter or chip driver, or
run sensors-detect and add the `ignore=' modprobe parameters it
suggests.

4.16 I ran sensors-detect, but now I get very strange readings?!?
=================================================================

Your SMBus (PIIX4?) is probably crashed or hung. There are some
mainboards which connect a clock chip to the SMBus. Unfortunately, this
clock chip hangs the PIIX4 if it is read (it is an I2C device, but not
SMBus compatible).  We have found no way of solving this, except for
rebooting your computer.  Next time when you run sensors-detect, you
may want to exclude addresses 0x69 and/or 0x6a, by entering `s' when
you are asked whether you want to scan the PIIX4.

4.17 Bad readings from particular chips
=======================================

See below for some particularly troublesome chips.  Also be sure and
check `doc/chips/xxxxx' for the particular driver.

4.17.1 Bad readings from the AS99127F!
--------------------------------------

The Asus AS99127F is a modified version of the Winbond W83781D.  Asus
will not release a datasheet. The driver was developed by tedious
experimentation. We've done the best we can. If you want to make
adjustments to the readings please edit `/etc/sensors.conf.' Please
don't ask us to fix the driver. Ask Asus to release a datasheet.

4.17.2 Bad readings from the VIA 686A!
--------------------------------------

The Via 686A datasheet is incomplete.  Via will not release details.
The driver was developed by tedious experimentation. We've done the
best we can. If you want to make adjustments to the readings please
edit `/etc/sensors.conf.' Please don't ask us to fix the driver. Ask
Via to release a better datasheet.  Also, don't forget to `modprobe
i2c-isa'.

4.17.3 Bad readings from the MTP008!
------------------------------------

The MTP008 has programmable temperature sensor types.  If your sensor
type does not match the default, you will have to change it.  See
`doc/chips/mtp008' for details.  Also, MTP008 chips seem to randomly
refuse to respond, for unknown reasons. You can see this as 'XX'
entries in i2cdump.

4.17.4 Bad temperature readings from the SIS5595!
-------------------------------------------------

This chip can use multiple thermistor types and there are also two
different versions of the chip. We are trying to get the driver working
better and develop formulas for different thermistors but we aren't
there yet. Sorry.  Also, many times the chip isn't really a sis5595 but
it was misidentified. We are working on improving that too.

4.17.5 Bad readings from a w8378[12]d!
--------------------------------------

Do you own an ASUS motherboard?  Perhaps your chip is being
misidentified.  Look on the motherboard (or at
`http://mbm.livewiredev.com') for a 'Winbond' or Asus chip.  Often the
real device is an Asus as99127f. If so, the driver can be forced to
recognize the as99127f with `force_as99127f=BUS,0x2d' where `BUS' is
your i2c bus number.  Cat /proc/bus/i2c to see a list of bus numbers.
Read the w83781d module documentation (`doc/chips/w83781d') for more
details.

4.17.6 Bus hangs on Ali 1543 on Asus P5A boards!
------------------------------------------------

The SMBus tends to hang on this board and it seems to get worse at
higher temperatures. Use ISA accesses to reliably use the w83781d
monitor chip on this board and use the `ignore=1,0x2d' or similar option
to the w83781d module to prevent i2c accesses.

4.17.7 Bad readings from LM75!
------------------------------

The LM75 detection is poor and other hardware is often misdetected as
an LM75. Figure out what you really have *Note What chips are on
motherboard XYZ: Section 3.2.1.

4.17.8 Bad readings from LM78!
------------------------------

The LM78 is no longer manufactured by National Semiconductor.  You
probably don't have a real LM78 but something similar that we do not
recogize or support. Figure out what you really have *Note What chips
are on motherboard XYZ: Section 3.2.1.

4.17.9 Bad readings from LM80!
------------------------------

The LM80 detection is poor and other hardware is often misdetected as
an LM80. Figure out what you really have *Note What chips are on
motherboard XYZ: Section 3.2.1.

4.18 How do I configure two chips (LM87) differently?
=====================================================

There is a SuperMicro board with two LM87's on it that are not hooked
up in the same way, so they need different defaults.  For example, both
CPU temperatures go to one LM87.

   Make two different sections in `/etc/sensors.conf' as follows:
     chip "lm87-i2c-*-2c"
         put configuration for the chip at 0x2c here
     chip "lm87-i2c-*-2d"
         put configuration for the chip at 0x2d here

   There is a commented example in `sensors.conf.eg' which should be
helpful.

4.19 Dmesg says `Upgrade BIOS'! I don't want to!
================================================

If the problem is a PCI device is not present in `lspci', the solution
is complex. For the ALI M7101 device, there is a solution which uses the
2.4 kernel's `hotplug' facility. See `prog/hotplug' in our package.
For other PCI devices, you can try to modify the m7101 solution in
`prog/hotplug'.

   If dmesg says `try force_addr', see below. Other drivers generally
do not support the force_addr parameter. Sorry. Check the documentation
for your driver in `doc/[chips,busses]' and if we don't support it you
can send us your request.

4.19.1 Dmesg says `use force_addr=0xaddr'! What address do I use?
-----------------------------------------------------------------

If the problem is a PCI device whose base address is not set, you may
be able to set the address with a force parameter. The via686a and
sis5595 chip drivers, and some bus drivers, support the command line
`modprobe via686a force_addr=0xADDRESS' where ADDRESS is the I/O
address. You must select an address that is not in use.  `cat
`/proc/ioports'' to check (carefully) for conflicts. A high number like
0xf000 is generally safe.

4.20 Sensors says `Can't access procfs/sysfs file'
==================================================

   * Linux 2.6
        * Did you `modprobe i2c_sensor'? Check `lsmod'.

        * Do you have sysfs support in your kernel and `/sys' mounted
          (is `/sys' there and populated)?  Create /sys with `mkdir
          /sys' if needed. Then add the following line to `/etc/fstab':
               sys              /sys             sysfs       default          0   0
          and `mount /sys'.

   * Linux 2.4
        * Did you `modprobe i2c-proc'? Check `lsmod'.

        * Do you have procfs support in your kernel and `/proc' mounted
          (is `/proc' there and populated)?  Create /proc with `mkdir
          /proc' if needed. Then add the following line to `/etc/fstab':
               proc             /proc            proc        defaults         0   0
          and `mount /proc'.

   * If you did `sensors -s', did you run it as root?

4.21 Sensors says `No sensors found!'
=====================================

   * Did `sensors-detect' find sensors? (If not *note Sensors-detect
     doesnt find any sensors::)

   * Did you do what `sensors-detect' said?

   * Did you `modprobe' your sensor modules?

   * Did you `modprobe' your I2C adapter modules?

   * Did you `modprobe i2c-isa' if you have ISA sensor chips?

   * Check `lsmod'.

4.22 Sensors output is not correct!
===================================

What specifically is the trouble?
   * Labels: *Note The labels for the voltage and temperature readings
     in sensors are incorrect: Section 3.4.1.

   * Min/max readings: *Note The min and max for the readings in
     sensors are incorrect: Section 3.4.2, and *Note The min and max
     settings didnt take effect: Section 3.4.3.

   * AS99127F: *Note I ran sensors-detect but now I get very strange
     readings?: Section 4.16.

   * Via 686A: *Note I ran sensors-detect but now I get very strange
     readings?: Section 4.16.

   * Other specific chips: *Note I ran sensors-detect but now I get
     very strange readings?: Section 4.16.

   * No output for a particular sensors chip: *Note What to do if it
     inserts but nothing happens: Section 5.3.

   * No output at all: *Note Sensors says No sensors found: Section
     4.21, *Note What to do if it inserts but nothing happens: Section
     5.3.

   * Completely bad output for a particular sensor chip: *Note What to
     do if I read only bogus information: Section 5.4.

   * One particular sensor readings:
        * Maybe it isn't hooked up? - tell 'sensors' to ignore it.
          *Note One sensor isnt hooked up on my board: Section 3.4.4.

        * Maybe it is hooked up differently on your motherboard? -
          adjust `sensors.conf' calculation.

4.23 What is at I2C address XXX?
================================

In general, we don't know. Start by running `sensors-detect'.  If it
doesn't recognize it, try running `i2cdump'. A partial list of
manufacturers' IDs are at the bottom of `doc/chips/SUMMARY'.

4.23.1 What is at I2C address 0x69?
-----------------------------------

A clock chip. Often, accessing these clock chips in the wrong way will
instantly crash your computer. Sensors-detect carefully avoids these
chips, and you should do too.  You have been warned.

4.23.2 What is at I2C addresses 0x50 - 0x57?
--------------------------------------------

EEPROMs on your SDRAM DIMMs. Load the eeprom module to look at some
basic data in `sensors' or use the program
`prog/eeprom/decode-dimms.pl' to get more information than you ever
wanted.

4.23.3 What is at I2C addresses 0x30 - 0x37?
--------------------------------------------

These are often 'shadows' of your EEPROMs on your SDRAM DIMMs at
addresses 0x50 - 0x57. They are the 'software write-protect' registers
of the SDRAM Serial Presence Detect EEPROMs.  If you try and do a
`i2cdump' on them to read the location, you won't get anything, because
they contain a single write-only register.  This register can be used
to permanently write-protect the contents of the eeprom.

4.24 Sensors-detect doesn't work at all
=======================================

It could be many things. What was the problem? *Note Problems on
particular motherboards: Section 4.31.

4.24.1 Sensors-detect says "Couldn't open /proc/bus/i2c?!?"
-----------------------------------------------------------

You don't have i2c support in your kernel, or the i2c-core module was
not loaded and you did not run sensors-detect as root.

4.24.2 Sensors-detect says "Can't open /dev/i2c[-/]0"
-----------------------------------------------------

Your `/dev/i2c-0,' `/dev/i2c0', or `/dev/i2c/0' files do not exist or
you did not run `sensors-detect' as root.  Run the script
`prog/mkdev/mkdev.sh' to create the `/dev/i2c-x' files.  Run `devfs' in
the kernel to get the `/dev/i2c/x' files.

4.24.3 Sensors-detect doesn't find any sensors!
-----------------------------------------------

Either
  1. The board doesn't have any sensors.

  2. We don't support the sensors on the board.

  3. The sensors it has are on an I2C bus connected to an I2C bus
     adapter that we don't support.

  4. You don't have the latest version of lm_sensors.

   But in any case you should figure out what is on the board:
  1. Look at your motherboard.

  2. Check the manufacturer's website.

  3. Check the Motherboard Monitor (http://mbm.livewiredev.com/)
     website.

   When you know what chips you have, check the Driver Status
(http://www.lm-sensors.org/wiki/Devices) web page to see if support has
been added for your chip in a later release or in SVN.

4.25 Sensors says `Error: Line xxx: zzzzzzz'
============================================

These are errors from the libsensors library in reading the
`/etc/sensors.conf' configuration file. Go to that line number and fix
it. If you have a parse error, perhaps you have to put the feature name
in double quotes.

4.26 Sensors only gives the name, adapter, and algorithm for my chip
====================================================================

If `sensors' only says this, for example, and doesn't provide any
actual data at all:

     it87-isa-0290
     Adapter: ISA adapter
     Algorithm: ISA algorithm

   Your chip is not currently supported by `sensors' and so all it does
is print out that information. Get the latest release and be sure you
are running the `sensors' program it installed and not some older
`sensors'.

4.27 Sensors says `ERROR: Can't get xxxxx data!'
================================================

   * (Linux 2.6) Make sure you are using one of the recommended
     kernel/lm_sensors combination
     (http://www.lm-sensors.org/wiki/Kernel2.6).

   * You have a `libsensors'/`sensors' mismatch.  `sensors' is unable to
     get a data entry from `libsensors'. You probably have an old
     `libsensors' in your `/etc/ld.so.conf' path.  Make sure you did
     (as root) a `make install' (Linux 2.4) or `make user_install'
     (Linux 2.6) followed by a `ldconfig'.  Then check the output of
     `ldconfig -v | grep libsensors' to verify that there is only ONE
     `libsensors' entry and that it matches the `libsensors' that was
     built in the `lib/' directory in `lm_sensors2'.

4.28 Sensors doesn't find any sensors, just eeproms.
====================================================

*Note Sensors-detect doesnt work at all: Section 4.24, if
`sensors-detect' failed to find any sensors.

   If `sensors-detect' did find sensors, did you insert your modules?
For chips on the ISA bus, did you insert i2c-isa?

   *Note What to do if a module wont insert: Section 5.2, if the
modules didn't insert, also *Note Sensors says No sensors found:
Section 4.21.

4.29 Inserting modules hangs my board
=====================================

There are several possible causes:
  1. Bus driver problems. Insert the bus driver first, before you have
     inserted any chip drivers, to verify.

  2. Wrong chip driver. Verify that you have a chip supported by the
     chip driver, see *Note What chips are on motherboard XYZ: Section
     3.2.1.

  3. The chip driver is reinitializing the chip, which undoes critical
     initialization done by the BIOS.  Try the parameter `init=0' for
     the w83781d driver; this is the only driver supporting this
     parameter.

  4. Some chips on the bus don't like to be probed at all.  After
     inserting the bus driver (but not the chip drivers), run
     `i2cdetect' on the bus, then `i2cdump' on each address responding
     to `i2cdetect'. This may find the culprit.  Do not `i2cdump
     address 0x69', the clock chip.

  5. The chip driver is incorrectly finding a second chip on the bus
     and is accessing it. For example, with the Tyan 2688 with a
     w83781d at 0x29, use `modprobe
     ignore_range=0,0x00,0x28,0,0x2a,0x7f' to prevent access to other
     addresses. (`init=0' also req'd for the Tyan 2688).

4.30 Inserting modules slows down my board
==========================================

Generally this is caused by an overtemperature alarm output from the
sensor chip. This triggers hardware on the board which automatically
slows down the CPU clock. Be sure that your temperature limits are
above the temperature reading. Put the new limits in