root/lm-sensors/trunk/doc/FAQ @ 1055

Sensors FAQ for lm_sensors version 2
------------------------------------

    Copyright (c) 1998, 1999, 2000, 2001  Frodo Looijaard <frodol@dds.nl>,
    Philip Edelbrock <phil@netroedge.com>, and Mark Studebaker <mdsxyz123@yahoo.com>

------------------------------------------------------------------------------------

CONTENTS

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 LMxx 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?
  3.2A What chips are on motherboard XYZ?
  3.2B Do you support motherboard XYZ?
  3.2C Do you support chip XYZ?
  3.2D Anybody working on a driver for chip XYZ?
3.3 Which modules should I insert?
3.4 Do I need the configuration file?
  3.4A The labels for the voltage and temperature readings in 'sensors' are incorrect!
  3.4B The min and max for the readings in 'sensors' are incorrect!
  3.4C The min and max settings in /etc/sensors.conf didn't take effect!
  3.4D One sensor isn't hooked up on my board!
3.5 What about the 'No such file or directory' warnings when I compile it?
3.6 I get all kind of weird compilation errors?
3.7 It still does not compile or patch

4 Problems
4.1 Why do my fans report exactly half/double their values by your code
compared to the BIOS? 
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 with my power
supply?
4.6 Some measurements are way out of range. What happened?
4.7 What are VID lines?
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?
  4.14A  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 the particular chips
  4.17A Bad readings from the AS99127F!
  4.17B Bad readings from the VIA 686A!
  4.17C Bad readings from the MTP008!
4.18 How do I configure two chips (LM87) differently?
4.19 Dmesg says Upgrade BIOS! I don't want to!
4.20 Sensors says 'Can't access /proc file'
4.21 Sensors says 'No sensors found!'
4.22 Sensors output is not correct!
4.23 What is at I2C address XXX?
  4.23A What is at I2C address 0x69?
  4.23B What is at I2C addresses 0x50 - 0x57?
  4.23C What is at I2C addresses 0x30 - 0x37?
4.24 Sensors-detect doesn't work at all
  4.24A Sensors-detect says "Couldn't open /proc/bus/i2c?!?"
  4.24B Sensors-detect says "Can't open /dev/i2c[-/]0"
  4.24C Sensors-detect doesn't find any sensors

5 How to Ask for Help  
5.1 What to do if a module won't insert?
5.2 What to do if it inserts, but nothing happens?
5.3 What to do if I read only bogus information?
5.4 What to do if you have other problems?
5.5 What if it just works like a charm?

6 Version 1 specific questions
6.1 My manufacturer swears that my mainboard has an SMBus, but your code 
reports that it can't find it.  What's wrong? 
6.2 The modules won't load, saying 'SMBus not detected'.
6.3 I try to read /proc/sensors, and I get a "No sensor data yet (try again in 
a few moments)" message. Why?

-------------------------------------------------------------


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://www2.lm-sensors.nu/~lm78/useful_addresses.html
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 in which the host must refer to it with. 
    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. See the file /proc/ioports for a list of devices living on
the "ISA Bus" in your system.


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 let 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.
    At this moment, interrupts are not supported.



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 go to section 5.


3.2A What chips are on motherboard XYZ?

    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.
        4) Check the Motherboard Monitor website
           (see useful_addresses.html) for a good cross-reference.


3.2B Do you support motherboard XYZ?

    See 3.2A.


3.2C Do you support chip XYZ?

    This we have good answers for.
        Sorted by Manufacturer:   README
        Sorted by Manufacturer:   http://www2.lm-sensors.nu/~lm78/supported.html
        Sorted by Sensor Driver:  doc/chips/SUMMARY
        Newest Driver Status:     http://www2.lm-sensors.nu/~lm78/newdrivers.html
        

3.2D Anybody working on a driver for chip XYZ?

        Newest Driver Status:     http://www2.lm-sensors.nu/~lm78/newdrivers.html


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 sensors.conf configuration file?

    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.


3.4A 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.


3.4B The min and max for the readings in 'sensors' are incorrect!

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


3.4C The min and max settings in /etc/sensors.conf didn't take effect!

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


3.4D One sensor isn't hooked up on my board!

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


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

    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.


3.7 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!



4 Problems
----------

4.1 Why do my fans report exactly half/double their values by your code
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:
    chip lm78-*               # Or whatever chip this relates to
    compute fan1 2*@,@/2      # Copy for each fan present


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.
    If you have an Asus P2B and want more information on adding thermal
sensing capability, check out:
http://ultimatepc.fsn.net/techinfo/p2bthermistor/p2bthermistor.htm
    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 (in upcoming versions) to make this reading
disappear.
    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'.
    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 with my power
supply?

    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. As long as they
stay within a sensible range (say 10% of the expected value), 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.


4.7 What are VID lines?

    These describe the voltage your processors use. This is supported
for most processors, however they are not always
correctly connected to the sensor chip, so the readings may be out of
range. A value of +3.5 V is especially suspect.


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 doc/useful_addresses.html 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 is just somewhere near it. 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


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'.


4.14A  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.


4.17A 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.


4.17B 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.


4.17C 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.


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


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 the problem is a PCI device whose base address is not set,
you may be able to set the address with a force parameter. For the via686a
driver, use the command line 'modprobe via686a force=9191,0xADDRESS' where
ADDRESS is the I/O address (cat /proc/ioports to verify you don't have
a conflict). Other drivers (for example sis5595) generally do not
support the force parameter. Sorry. You can send us your request.


4.20 Sensors says 'Can't access /proc file'

    Did you 'modprobe sensors'? Check 'lsmod'.


4.21 Sensors says 'No sensors found!'

    Did sensors-detect find sensors? (If not see 4.23C)
    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: See 3.4A above.
        Min/max readings: See 3.4B&C above.
        AS99127F: See 4.17 above
        Via 686A: See 4.18 above
        No output for a particular sensors chip: See 5.2 below
        No output at all: See 4.21, 4.22 above; 5.2 below
        Completely bad output for a particular sensor chip: See 5.3 below
        One particular sensor readings:
            Maybe it isn't hooked up;
                tell 'sensors' to ignore it. See 3.4D above.
            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.


4.23A 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. If you really really want to play with your clock
chip you can look at kernel/chips/icspll.c in our package. But we
do not recommend it. You have been warned.


4.23B 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.


4.23C What is at I2C addresses 0x30 - 0x37?

    These are often 'shadows' of you EEPROMs on your SDRAM DIMMs
at addresses 0x50 - 0x57. They aren't really there. If you try and
do a 'i2cdump' on them you won't get anything. This is probably
caused by some timing problem on your motherboard or on the DIMMs.
We don't know the exact cause.


4.24 Sensors-detect doesn't work at all

    It could be many things. What was the problem? See below
    in questions 4.24 A-C.


4.24A 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.


4.24B 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.


4.24C 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.
    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 website
           (see useful_addresses.html) for a good cross-reference.


5 How to ask for help
---------------------

    We are always willing to answer questions if things don't work out.
Please mail sensors@stimpy.netroedge.com, and not the individual authors,
unless you have something private to say.
    Instead of using email, you can also use the web-based support
area, at http://www.netroedge.com/~lm78/support.html. You will be helped
just as fast, and others may profit from the answer too. You will be
noticed automatically when your question has been answered.

    Here's what you should send us:

    - The dmesg or syslog output if applicable
    - The output of (as root) 'prog/detect/sensors-detect'
    - The output of 'lsmod'
    - If a PCI chip problem:
        * The output of 'lspci' or 'cat /proc/pci'
    - If a I2C sensor chip problem:
        * The output of (as root) 'prog/detect/i2cdetect X'
              X = the bus number
              (run 'i2cdetect' with no arguments to list the busses)
        * The output of (as root) 'prog/dump/i2cdump X 0xXX'
              XX = the address of each chip you see in the output
              of i2cdetect. (run once for each chip)
    - If a ISA sensor chip problem:
        * The output of (as root) 'prog/dump/isadump 0x295 0x296'
    - Part numbers of chips on your motherboard you think are
          the sensor chips (look at your motherboard)
    - Motherboard type
    - Sensors version
    - Kernel version


5.1 What to do if a module won't insert?

    Did you use 'modprobe' instead of 'insmod'??? Don't use insmod.
    Were there unresolved symbols? Did you run 'depmod -a'? Run
'depmod -a -e' to see where the symbol problem is.
    Always inspect the output of 'dmesg'. That's where the error
messages come out. Don't rely on the generic message from 'modprobe'.
If you still can't figure it out, send us the information
listed above.


5.2 What to do if it inserts, but nothing happens?

    For an ISA sensor chip, did you also 'modprobe i2c-isa'? It must be inserted.
    For an I2C sensor chip, did you also 'modprobe i2c-xxx' where xxx is your
I2C bus adapter? It must be inserted.
    Always inspect the output of 'dmesg'. That's where the error
messages come out. If you still can't figure it out, send us the information
listed above.


5.3 What to do if I read only bogus information?

    It may be that this was a mis-detection: the chip may not be
present. If you are convinced there is something wrong, verify that you
indeed have the devices on your motherboard that you think you do.
Look at the motherboard and make sure. If you are still stuck,
please send us the usual information (see section 5).


5.4 What to do if you have other problems?

    Again, send the output listed above.


5.5 What if it just works like a charm?

    Drop us a mail if you feel like it, mentioning the mainboard and
detected chip type. That way, we have some positive feedback, too!



6 Version 1 specific questions
------------------------------

Note: Version 1 is very very old and is not recommended.

6.1 My manufacturer swears that my mainboard has an SMBus, but your code 
reports that it can't find it.  What's wrong? 

    Currently, our code only assumes that an SMBus exists if it originates 
from the Intel PIIX4 (82371AB).  If your computer doesn't have one, or if your 
SMBus originates from a different SMBus 'host', then you are out of luck. :'( 
Our experience is, though, that most machines have a PIIX4, and that it is 
where the SMBus is hosted.

Regarding the VIA chip set(s):
    Right now, the SMBus code depends on the Intel PIIX4 chip to handle 
SMBus transactions.  The VIA chip set is NOT supported at this time because 
it forces much of the SMBus protocol to be implemented by software.
    To implement the SMBus correctly with the VIA chip, it needs to be 
written at a low level to be quick.  A more attractive alternative is to 
use the Bios SMBus interface (not always available nor standard).

    Version 2 supports the VIA chipset, and will support other chipsets.
Version 1 never will.


6.2 The modules won't load, saying 'SMBus not detected'.

    This should no longer be an issue in 1.4.10 and later; it will
continue loading, but it won't support SMBus-connected devices, of course.


6.3 I try to read /proc/sensors, and I get a "No sensor data yet (try again in 
a few moments)" message. Why?

    It takes about 1.5 seconds for the LM78 to update all its sensor 
values.  If we would try to read it before it finished that, you would get
old garbage instead. So you have to wait 1.5 seconds after the module is
inserted before you can access /proc/sensors.
    Module versions 1.3.7 and later let the process sleep if it tries
to access sensor data right after insertion time, and do not display this
message anymore.


6.4 On my Dell, a LM80 is detected, but all readings are 0!

    This is a bug we have only observed on Dell computers. There is
probably a problem with the way the SMBus is accessed; but it is not yet
clear whether the problem is in our code or with the Dells.
    There are very probably no sensor chips at all on your computer;
but until somebody contacts Dell about this and tells us the results, we
can not be sure.


---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
Rev 2.3 (MDS) General update, 20010224
Rev 2.2 (Frodo) Corrections for lm_sensors 2.4, 19990920
Rev 2.1 (Frodo) Corrections for lm_sensors 2.2, 19990112
Rev 2.0 (Frodo) Major revision for lm_sensors 2.1, 19981229
Rev 1.10 (Frodo) Modified 3.8, updated some other things, 19980924
Rev 1.9 (Frodo) Added 3.15, 19980906
Rev 1.8 (Frodo) Added 3.14, 19980905
Rev 1.7 (Phil) Added 3.13 and some other minor changes, 19980901
Rev 1.6 (Frodo) Added 4, 4.1, 4.2, 4.3, 4.4, 4.5, 19980901
Rev 1.5 (Frodo) Added 2.3, 2.4, 3.9, 3.10, 3.11, 19980826
Rev 1.4 (Frodo) Added some more Winbond information, and 3.5-3.8, 19980817
Rev 1.3 Added info on the Winbond chip, 19980816
Rev 1.2 Adapation by Frodo Looijaard, 19980810
Rev 1.1 Modifications by Philip Edelbrock, 19980809
Rev 1.0 Written by Philip Edelbrock, 19980803