root/lm-sensors/tags/V2-10-2/doc/lm_sensors-FAQ.texi

\input texinfo.tex    @c -*-texinfo-*-

@c %**start of header
@setfilename lm_sensors-FAQ.info
@include version.texi
@settitle Sensors FAQ for lm_sensors version @value{VERSION}
@comment %**end of header

@titlepage
@center @titlefont{This is the FAQ for the @command{lm_sensors} program, @value{VERSION}}
@sp 3
@center Copyright (C) 1998 - 2005
@sp 1
@center Frodo Looijaard,
@center Philip Edelbrock,
@center Mark D. Studebaker,
@center and
@center Jean Delvare
@end titlepage

@ifhtml
Copyright (C) 1998 - 2005@*
Frodo Looijaard,@*
Philip Edelbrock,@*
Mark D. Studebaker@*
and@*
Jean Delvare@*
@end ifhtml

@dircategory Utilities
@direntry
* lm_sensors-FAQ: (lm_sensors-FAQ)           The lm_sensors FAQ
@end direntry

@summarycontents
@contents

@ifnottex
@node Top
@top 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.

@end ifnottex

@menu
* Overview::                PC and Sensor Overview
* Basics::                  Sensor and Bus Basics
* Installation::            Installation and Management
* Problems::                Problems
* Help::                    How to Ask for Help
* Contribute::              How to Contribute
* Document Revisions::      Revision History of This Document
@end menu


@node Overview, Basics, Top, Top
@chapter PC and Sensor Overview

@menu
* Section 1.1::             What sensors are available on my PC? 
* Section 1.2::             What can a sensor chip like the "LM78" do?
* Section 1.3::             Where do I find out more about any of these chips?
@end menu

@node Section 1.1, Section 1.2, , Overview
@section 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.


@node Section 1.2, Section 1.3, Section 1.1, Overview
@section 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 @file{doc/chips} directory.


@node Section 1.3,  , Section 1.2, Overview
@section 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:

@itemize @bullet
  @item @uref{http://www.analog.com}
  @item @uref{http://www.dalsemi.com}
  @item @uref{http://www.maxim-ic.com}
  @item @uref{http://www.national.com}
@end itemize

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



@node Basics, Installation, Overview, Top
@chapter Sensor and Bus Basics

@menu
* Section 2.1::             What sensors are available on my PC? 
* Section 2.2::             What can a sensor chip like the "LM78" do?
* Section 2.3::             Where do I find out more about any of these chips?
* Section 2.4::             What sensors are available on my PC? 
* Section 2.5::             What can a sensor chip like the "LM78" do?
* Section 2.6::             Where do I find out more about any of these chips?
@end menu


@node Section 2.1, Section 2.2, , Basics
@section How are these sensors read?

Sensor chips reside on either the ISA bus, the SMBus, or both.
See the file @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.


@node Section 2.2, Section 2.3, Section 2.1, Basics
@section 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 @dfn{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.


@node Section 2.3, Section 2.4, Section 2.2, Basics
@section 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 @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".


@node Section 2.4, Section 2.5, Section 2.3, Basics
@section 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 @file{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.


@node Section 2.5, Section 2.6, Section 2.4, Basics
@section 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.


@node Section 2.6, , Section 2.5, Basics
@section 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 @file{/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.



@node Installation, Problems, Basics, Top
@chapter Installation and Management

@menu
* Section 3.1::     Why so many modules, and how do I cope with them?
* Section 3.2::     How do I know which chips I own?
* Section 3.3::     Which modules should I insert?
* Section 3.4::     Do I need the configuration file @file{/etc/sensors.conf}?
* Section 3.5::     What about the @samp{No such file or directory} warnings
* Section 3.6::     I get all kinds of weird compilation errors?
* Section 3.7::     It still does not compile or patch!
* Section 3.8::     @command{make install} fails on Mandrake kernels
* Section 3.9::     I get unresolved symbols when I @command{modprobe} modules
* Section 3.10::    I2C_DRIVERID_ADM1024 undefined (Red Hat especially)
@end menu

@node Section 3.1, Section 3.2, , Installation
@section 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:
@itemize
  @item Run @command{sensors-detect} and do what it tells you.
  @item Always use @command{modprobe}, not @command{insmod}.
@end itemize

Further information is in @file{doc/modules}.


@anchor{How do I know which chips I own}
@node Section 3.2, Section 3.3, Section 3.1, Installation
@section How do I know which chips I own?

We have an excellent program that scans all your hardware.
It is called @file{sensors-detect} and is installed in @file{/usr/local/sbin}
by @command{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 @pxref{Help})


@anchor{Section 3.2.1}
@subsection What chips are on motherboard XYZ?

    @strong{!!!!!!!!! YES THIS IS THE MOST FREQUENT QUESTION WE GET !!!!!!!!!}

We have no idea. Here is what you should do:
@enumerate
  @item Run sensors-detect.
@end enumerate

If that doesn't work:
@enumerate 2
@item Look at your motherboard.
@item Check the manufacturer's website or ask their support
@item Check the @uref{http://mbm.livewiredev.com/, Motherboard Monitor} website and the
@uref{http://www.lm-sensors.org/wiki/UsefulLinks, "links"}
page on @uref{http://www.lm-sensors.org, our website} some good cross-references.
@end enumerate


@anchor{Section 3.2.2}
@subsection Do you support motherboard XYZ?

We don't support boards, we support chips. @xref{Section 3.2.1, What chips are on motherboard XYZ}.


@anchor{Section 3.2.3}
@subsection Do you support chip XYZ?

This we have good answers for.
@itemize
@item Sorted by Manufacturer:   @file{README}
@item Sorted by Manufacturer:   @uref{http://www.lm-sensors.org/wiki/Devices}
@item Sorted by Sensor Driver:  @file{doc/chips/SUMMARY}
@end itemize


@anchor{Section 3.2.4}
@subsection Anybody working on a driver for chip XYZ?

Newest Driver Status: @uref{http://www.lm-sensors.org/wiki/Devices}


@node Section 3.3, Section 3.4, Section 3.2, Installation
@section Which modules should I insert?

@command{sensors-detect} will tell you. Take the @command{modprobe} lines it
recommends and paste them into the appropriate @file{/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 @file{i2c-isa.o}.
for each type of chip you own. That's all. On my computer, I could use the
following lines:
@itemize
@item @command{modprobe i2c-isa}
@item @command{modprobe i2c-piix4}
@item @command{modprobe lm78}
@item @command{modprobe lm75}
@item @command{modprobe i2c-dev}
@item @command{sensors -s}
@end itemize


@node Section 3.4, Section 3.5, Section 3.3, Installation
@section Do I need the configuration file @file{/etc/sensors.conf}?

Yes, for any applications that use @file{libsensors,} including the
@command{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 @file{/etc/sensors.conf}, but it will not
overwrite any existing file with that name.


@anchor{Section 3.4.1}
@subsection The labels for the voltage and temperature readings in @command{sensors} are incorrect!

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


@anchor{Section 3.4.2}
@subsection The min and max for the readings in @command{sensors} are incorrect!

You can customize them in the file @file{/etc/sensors.conf}. See above.


@anchor{Section 3.4.3}
@subsection The min and max settings in @file{/etc/sensors.conf} didn't take effect!

You forgot to run @command{sensors -s}. See above.


@anchor{Section 3.4.4}
@subsection One sensor isn't hooked up on my board!

Use an @command{ignore} line in @file{/etc/sensors.conf} so it isn't
displayed in @command{sensors}.


@anchor{Section 3.4.5}
@subsection I need help with @file{sensors.conf}!

There is detailed help at the top of that file.


@anchor{Section 3.4.6}
@subsection Do you have a database of @file{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.


@node Section 3.5, Section 3.6, Section 3.4, Installation
@section What about the @samp{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 @command{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.


@node Section 3.6, Section 3.7, Section 3.5, Installation
@section 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 @file{/usr/local/include} or
@file{/usr/src/linux*/include}. Try to edit the @file{Makefile} for the other setting.


@anchor{Section 3.6.1}
@subsection @samp{No rule to make target xxxx needed by xxxx} - how to fix?

@itemize
@item @xref{Section 3.6, I get all kinds of weird compilation errors}, also try @command{make clean} in @file{lm_sensors}.
@item If that doesn't work, try @command{make clean} in @file{i2c}.
@item If that doesn't work, try @command{make clean} in the kernel.
@item Also make sure @file{/usr/include/linux} points to @file{/usr/src/linux/include/linux}.
@end itemize


@node Section 3.7, Section 3.8, Section 3.6, Installation
@section 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!


@node Section 3.8, Section 3.9, Section 3.7, Installation
@section @command{make install} fails on Mandrake kernels

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


@node Section 3.9, Section 3.10, Section 3.8, Installation
@section I get unresolved symbols when I @command{modprobe} modules (Red Hat especially)

Example:
@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
@end example

You can also run @command{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 @command{make LINUX=/usr/src/linux-2.4.14}.


Try the following to be sure:

@itemize
@item @command{nm --extern MODULE.o}
Filter out the kernel symbols, like @code{kmalloc}, @code{printk} etc. and note the
number code behind them, like @code{printk_R1b7d4074}. If there is no numeric
code after them, note this too.
@item @command{grep SYMBOL /proc/ksyms}
Substitute SYMBOL by the basename of the symbols above, like @code{kmalloc},
@code{printk} etc. Note the number code behind them, or the lack thereof.
@item 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.
@end itemize


@node Section 3.10, , Section 3.9, Installation
@section 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:

@enumerate
@item @command{rpm -qa | grep i2c}
@item Look for @file{kernel-i2c,} or a similar rpm in the output
@item <as root>
@command{rpm -ev kernel-i2c} (or the name of the similar package)
If this complains about dependencies, you can try adding
@command{--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.
@item Try (in the build directory of @file{lm_sensors)}
@example
@command{make clean}
@command{make}
@end example
@item @emph{If} you still have problems, you may have to replace the include
paths in the @file{.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.
@end enumerate


@node Problems, Help, Installation, Top
@chapter Problems

@menu
* Section 4.1::         My fans report exactly half/double their values?
* Section 4.2::         Why do my two LM75's report "-48 degrees"?
* Section 4.3::         Why do I have two Vcore readings?
* Section 4.4::         How do those ALARMS work?
* Section 4.5::         My voltage readings seem to drift a bit. What's wrong?
* Section 4.6::         Some measurements are way out of range. What happened?
* Section 4.7::         What are VID lines? Why is the VID reading wrong?
* Section 4.8::         Sensor are only updated each second or so. Why?
* Section 4.9::         It takes a second before reading sensor results. Why?
* Section 4.10::        Can I be alerted when an ALARM occurs?
* Section 4.11::        SMBus transactions on my PIIX4 simply don't work. Why?
* Section 4.12::        My BIOS reports a higher CPU temperature than you!
* Section 4.13::        I read strange values from the raw @file{/proc} files!
* Section 4.14::        How do I set new limits?
* Section 4.15::        Some sensors are doubly detected?
* Section 4.16::        I ran sensors-detect, but now I get strange readings?!
* Section 4.17::        Bad readings from particular chips
* Section 4.18::        How do I configure two chips (LM87) differently?
* Section 4.19::        Dmesg says @samp{Upgrade BIOS}! I don't want to!
* Section 4.20::        Sensors says @samp{Can't access procfs/sysfs file}
* Section 4.21::        Sensors says @samp{No sensors found!}
* Section 4.22::        Sensors output is not correct!
* Section 4.23::        What is at I2C address XXX?
* Section 4.24::        Sensors-detect doesn't work at all
* Section 4.25::        Sensors says @samp{Error: Line xxx: zzzzzzz}
* Section 4.26::        Sensors only gives the name, adapter, and algorithm!
* Section 4.27::        Sensors says @samp{ERROR: Can't get xxxxx data!}
* Section 4.28::        Sensors doesn't find any sensors, just eeproms.
* Section 4.29::        Inserting modules hangs my board
* Section 4.30::        Inserting modules slows down my board
* Section 4.31::        Problems on particular motherboards
* Section 4.32::        Problems on particular systems
* Section 4.33::        Problems on 2.6 kernels
@end menu


@node Section 4.1, Section 4.2, , Problems
@section 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 @file{/etc/sensors.conf}:

@example
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
@end example

See @file{doc/fan-divisors} in our package for further information.


@anchor{Fans sometimes/always read 0!}
@subsection 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 @file{doc/fan-divisors}
in our package for further information.


@anchor{I doubled the fan divisor and the fan still reads 7000}
@subsection 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 @file{/etc/sensors.conf}.
@xref{Section 4.1, My fans report exactly half/double their values compared to the BIOS},
and see @file{doc/fan-divisors} in our package for further information.


@node Section 4.2, Section 4.3, Section 4.1, Problems
@section 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.


@node Section 4.3, Section 4.4, Section 4.2, Problems
@section 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 @command{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.


@node Section 4.4, Section 4.5, Section 4.3, Problems
@section How do those ALARMS work? The current value is within range but there is still an ALARM warning!

The ALARM indications in @command{sensors} are those reported by the
sensor chip itself. They are NOT calculated by @command{sensors}. @command{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 @file{doc/chips} and the
chip datasheet for more information.


@node Section 4.5, Section 4.6, Section 4.4, Problems
@section 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.


@node Section 4.6, Section 4.7, Section 4.5, Problems
@section 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.

@anchor{-5V and -12V readings are way out of range!}
@subsection -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
@command{ignore inN} lines to @file{/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.


@node Section 4.7, Section 4.8, Section 4.6, Problems
@section 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 @command{ignore vid} to @file{/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 @file{/etc/sensors.conf}.
See @file{doc/vid} for more information.


@node Section 4.8, Section 4.9, Section 4.7, Problems
@section 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).


@node Section 4.9, Section 4.10, Section 4.8, Problems
@section 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.


@node Section 4.10, Section 4.11, Section 4.9, Problems
@section 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 @uref{http://www.lm-sensors.org/wiki/UsefulLinks} for addresses.


@node Section 4.11, Section 4.12, Section 4.10, Problems
@section 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.


@node Section 4.12, Section 4.13, Section 4.11, Problems
@section 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:

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

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.

@node Section 4.13, Section 4.14, Section 4.12, Problems
@section I try to read the raw @file{/proc} files, but the values are strange?!?

Remember, these values do not take the configuration file
@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 @command{sensors} program) instead.


@node Section 4.14, Section 4.15, Section 4.13, Problems
@section How do I set new limits?

Change the limit values in @file{/etc/sensors.conf} and then run
@command{sensors -s}.


@anchor{I set new limits and it didnt work}
@subsection  I set new limits and it didn't work?

You forgot to run @command{sensors -s}. Put it in a @file{/etc/rc.d/...} file
after the modprobe lines to run at startup.


@node Section 4.15, Section 4.16, Section 4.14, Problems
@section 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 @command{ignore=} modprobe parameters it suggests.


@node Section 4.16, Section 4.17, Section 4.15, Problems
@section 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 @kbd{s} when you are asked whether you want to
scan the PIIX4.


@node Section 4.17, Section 4.18, Section 4.16, Problems
@section Bad readings from particular chips

See below for some particularly troublesome chips.
Also be sure and check @file{doc/chips/xxxxx} for the particular driver.


@anchor{Bad readings from the AS99127F}
@subsection 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 @file{/etc/sensors.conf.} Please don't ask us to
fix the driver. Ask Asus to release a datasheet.


@anchor{Bad readings from the VIA 686A}
@subsection 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 @file{/etc/sensors.conf.} Please don't ask us to
fix the driver. Ask Via to release a better datasheet.
Also, don't forget to @command{modprobe i2c-isa}.


@anchor{Bad readings from the MTP008}
@subsection 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 @file{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.


@anchor{Bad temperature readings from the SIS5595}
@subsection 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.


@anchor{Bad readings from a w8378[12]d}
@subsection 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
@uref{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
@command{force_as99127f=BUS,0x2d} where @code{BUS} is your i2c bus number.
Cat /proc/bus/i2c to see a list of bus numbers.
Read the w83781d module documentation (@file{doc/chips/w83781d})
for more details.


@anchor{Bus hangs on Ali 1543 on Asus P5A boards}
@subsection 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 @command{ignore=1,0x2d} or similar option
to the w83781d module to prevent i2c accesses.


@anchor{Bad readings from LM75}
@subsection Bad readings from LM75!

The LM75 detection is poor and other hardware is often misdetected
as an LM75. Figure out what you really have @xref{Section 3.2.1, What chips are on motherboard XYZ}.


@anchor{Bad readings from LM78}
@subsection 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 @xref{Section 3.2.1, What chips are on motherboard XYZ}.


@anchor{Bad readings from LM80}
@subsection Bad readings from LM80!

The LM80 detection is poor and other hardware is often misdetected
as an LM80. Figure out what you really have @xref{Section 3.2.1, What chips are on motherboard XYZ}.


@node Section 4.18, Section 4.19, Section 4.17, Problems
@section 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 @file{/etc/sensors.conf} as follows:
@example
chip "lm87-i2c-*-2c"
    put configuration for the chip at 0x2c here
chip "lm87-i2c-*-2d"
    put configuration for the chip at 0x2d here
@end example

There is a commented example in @file{sensors.conf.eg} which should
be helpful.


@node Section 4.19, Section 4.20, Section 4.18, Problems
@section Dmesg says @samp{Upgrade BIOS}! I don't want to!

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


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


@anchor{Dmesg says use force_addr=0xaddr! What address do I use}
@subsection Dmesg says @samp{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
@command{modprobe via686a force_addr=0xADDRESS} where ADDRESS
is the I/O address. You must select an address that is not in use.
@command{cat @file{/proc/ioports}} to check (carefully) for conflicts. A high number like
0xf000 is generally safe.


@node Section 4.20, Section 4.21, Section 4.19, Problems
@section Sensors says @samp{Can't access procfs/sysfs file}

@itemize
@item Linux 2.6
@itemize 
@item Did you @command{modprobe i2c_sensor}? Check @command{lsmod}.
@item Do you have sysfs support in your kernel and @file{/sys} mounted (is @file{/sys} there and populated)?
Create /sys with @command{mkdir /sys} if needed. Then add the following line to @file{/etc/fstab}:
@example
sys              /sys             sysfs       default          0   0@end example
and @command{mount /sys}.
@end itemize
@item Linux 2.4
@itemize
@item Did you @command{modprobe i2c-proc}? Check @command{lsmod}.
@item Do you have procfs support in your kernel and @file{/proc} mounted (is @file{/proc} there and populated)?
Create /proc with @command{mkdir /proc} if needed. Then add the following line to @file{/etc/fstab}:
@example
proc             /proc            proc        defaults         0   0@end example
and @command{mount /proc}.
@end itemize
@item If you did @command{sensors -s}, did you run it as root?
@end itemize


@node Section 4.21, Section 4.22, Section 4.20, Problems
@section Sensors says @samp{No sensors found!}

@itemize
@item Did @command{sensors-detect} find sensors? (If not @pxref{Sensors-detect doesnt find any sensors})
@item Did you do what @command{sensors-detect} said?
@item Did you @command{modprobe} your sensor modules?
@item Did you @command{modprobe} your I2C adapter modules?
@item Did you @command{modprobe i2c-isa} if you have ISA sensor chips?
@item Check @command{lsmod}.
@end itemize


@node Section 4.22, Section 4.23, Section 4.21, Problems
@section Sensors output is not correct!

    What specifically is the trouble?
@itemize
@item Labels: @xref{Section 3.4.1, The labels for the voltage and temperature readings in sensors are incorrect}.
@item Min/max readings: @xref{Section 3.4.2, The min and max for the readings in sensors are incorrect}, and @xref{Section 3.4.3, The min and max settings didnt take effect}.
@item AS99127F: @xref{Section 4.16, I ran sensors-detect but now I get very strange readings?}.
@item Via 686A: @xref{Section 4.16, I ran sensors-detect but now I get very strange readings?}.
@item Other specific chips: @xref{Section 4.16, I ran sensors-detect but now I get very strange readings?}.
@item No output for a particular sensors chip: @xref{Section 5.3, What to do if it inserts but nothing happens}.
@item No output at all: @xref{Section 4.21, Sensors says No sensors found}, @xref{Section 5.3, What to do if it inserts but nothing happens}.
@item Completely bad output for a particular sensor chip: @xref{Section 5.4, What to do if I read only bogus information}.
@item One particular sensor readings:
@itemize
@item Maybe it isn't hooked up? - tell 'sensors' to ignore it. @xref{Section 3.4.4, One sensor isnt hooked up on my board}.
@item Maybe it is hooked up differently on your motherboard? - adjust @file{sensors.conf} calculation.
@end itemize
@end itemize

@node Section 4.23, Section 4.24, Section 4.22, Problems
@section What is at I2C address XXX?

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


@anchor{What is at I2C address 0x69}
@subsection 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.


@anchor{What is at I2C addresses 0x50 - 0x57}
@subsection What is at I2C addresses 0x50 - 0x57?

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


@anchor{What is at I2C addresses 0x30 - 0x37}
@subsection 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 @command{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.


@node Section 4.24, Section 4.25, Section 4.23, Problems
@section Sensors-detect doesn't work at all

It could be many things. What was the problem? @xref{Section 4.31, Problems on particular motherboards}.


@anchor{Sensors-detect says "Couldnt open /proc/bus/i2c?!?"}
@subsection 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.


@anchor{Sensors-detect says "Cant open /dev/i2c[-/]0"}
@subsection Sensors-detect says "Can't open /dev/i2c[-/]0"

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


@anchor{Sensors-detect doesnt find any sensors}
@subsection Sensors-detect doesn't find any sensors!

Either
@enumerate
@item The board doesn't have any sensors.
@item We don't support the sensors on the board.
@item The sensors it has are on an I2C bus connected to an I2C bus adapter that we don't support.
@item You don't have the latest version of lm_sensors.
@end enumerate

But in any case you should figure out what is on the board:
@enumerate
@item Look at your motherboard.
@item Check the manufacturer's website.
@item Check the @uref{http://mbm.livewiredev.com/, Motherboard Monitor} website.
@end enumerate

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


@node Section 4.25, Section 4.26, Section 4.24, Problems
@section Sensors says @samp{Error: Line xxx: zzzzzzz}

These are errors from the libsensors library in
reading the @file{/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.


@node Section 4.26, Section 4.27, Section 4.25, Problems
@section Sensors only gives the name, adapter, and algorithm for my chip

If @command{sensors} only says this, for example, and doesn't
provide any actual data at all:

@example
it87-isa-0290
Adapter: ISA adapter
Algorithm: ISA algorithm
@end example

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


@node Section 4.27, Section 4.28, Section 4.26, Problems
@section Sensors says @samp{ERROR: Can't get xxxxx data!}

@itemize
@item (Linux 2.6) Make sure you are using one of the
@uref{http://www.lm-sensors.org/wiki/Kernel2.6,
recommended kernel/lm_sensors combination}.
@item You have a @file{libsensors}/@command{sensors} mismatch.
@command{sensors} is unable to
get a data entry from @file{libsensors}. You probably have an
old @file{libsensors} in your @file{/etc/ld.so.conf} path.
Make sure you did (as root) a @command{make install} (Linux 2.4) or
@command{make user_install} (Linux 2.6) followed by a @command{ldconfig}.
Then check the output of @command{ldconfig -v | grep libsensors} to
verify that there is only ONE @file{libsensors} entry and that it matches
the @file{libsensors} that was built in the @file{lib/} directory in @file{lm_sensors2}.
@end itemize


@node Section 4.28, Section 4.29, Section 4.27, Problems
@section Sensors doesn't find any sensors, just eeproms.

@xref{Section 4.24, Sensors-detect doesnt work at all}, if @command{sensors-detect} failed to find any sensors.

If @command{sensors-detect} did find sensors, did you insert your modules? For chips on the ISA
bus, did you insert i2c-isa?

@xref{Section 5.2, What to do if a module wont insert}, if the modules didn't insert,
also @ref{Section 4.21, Sensors says No sensors found}.


@node Section 4.29, Section 4.30, Section 4.28, Problems
@section Inserting modules hangs my board

There are several possible causes:
@enumerate
@item Bus driver problems. Insert the bus driver first, before you have inserted any chip drivers, to verify.
@item Wrong chip driver. Verify that you have a chip supported by the chip driver, see @ref{Section 3.2.1, What chips are on motherboard XYZ}.
@item The chip driver is reinitializing the chip, which undoes critical initialization done by the BIOS.  Try the parameter @command{init=0} for the w83781d driver; this is the only driver supporting this parameter.
@item Some chips on the bus don't like to be probed at all.  After inserting the bus driver (but not the chip drivers), run @command{i2cdetect} on the bus, then @command{i2cdump} on each address responding to @command{i2cdetect}. This may find the culprit.  Do not @command{i2cdump address 0x69}, the clock chip.
@item 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 @command{modprobe ignore_range=0,0x00,0x28,0,0x2a,0x7f} to prevent access to other addresses. (@command{init=0} also req'd for the Tyan 2688).
@end enumerate