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@@ -1,10 +1,12 @@
Sensors FAQ for lm_sensors version 2
------------------------------------
[Internal comments/questions/uncertainties are in square brackets.]
Copyright (c) 1998, 1999, 2000, 2001 Frodo Looijaard <frodol@dds.nl>,
Philip Edelbrock <phil@netroedge.com>, and Mark Studebaker <mdsxyz123@yahoo.com>
Note: some questions were specific for version 1. These are put together
under chapter 6: version 1 questions.
------------------------------------------------------------------------------------
CONTENTS
1 What sensors are available on my PC?
1.1 What can a sensor chip like the "LM78" do?
@@ -12,15 +14,20 @@ under chapter 6: version 1 questions.
2 How are these sensors read?
2.1 What is the SMBus? And the I2C bus?
2.2 What sensors does the Pentium 2 (and P6) have?
2.2 What sensors do processors have?
2.3 How often are the sensor values updated?
2.4 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?
3.3 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
@@ -45,11 +52,21 @@ sensor reading results. 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 AS99127F!
4.18 Bad readings from the VIA 686A!
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 0x69?
4.24 What is at I2C addresses 0x50 - 0x57?
4.25 What is at I2C addresses 0x30 - 0x37?
5 How to ask for help:
5.1 What to do if it won't insert?
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?
@@ -64,17 +81,23 @@ a few moments)" message. Why?
-------------------------------------------------------------
1 What sensors are available on my PC?
Most medium/high-end computers since late 1997 now come with a LM78- or
LM79-like hardware health monitoring chip and an SMBus.
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.
1.1 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 12+/-V and 5+/-V supplies to
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
@@ -86,31 +109,36 @@ 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 should be documented somewhere in the doc/chips directory.
chip is documented in the doc/chips directory.
1.2 Where do I find out more about any of these LMxx chips?
1.2 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.
National Semiconductor has an excellent documentation resource on their
web-site. Complete specs on the LMxx chips talked about in this FAQ can be
downloaded at:
http://www.national.com
The Winbond documentation for Wxxxxxxx chips can be found at:
http://www.winbond.com.tw/produ/perso7.htm
The Genesys Logic documentation for GLxxxxx chips is regrettably not freely
downloadable.
Please see the file doc/useful_addresses.html for hyperlinks to
the available documentation.
2 How are these sensors read?
The LM78 and most other chips sensors are usually read through
the ISA bus. Our code looks for the presence of the chips on the ISA bus
and attempts to read the sensors from it by reading their different internal
registers.
Many chips have also, or even exclusively, an SMBus interface,
explained more in detail below.
-----------------------------
Sensor chips reside on either the ISA bus, the SMBus, or both.
See the file doc/chips/SUMMARY in our package for a list.
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 in your system.
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.
2.1 What is the SMBus? And the I2C bus?
@@ -132,8 +160,19 @@ the SMBus protocol in terms of I2C operations. But these hosts can also
talk to pure I2C devices.
2.2 What sensors does the Pentium 2 (and P6) have?
2.2 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
@@ -142,17 +181,12 @@ 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.
Apparently, the SEC connector has connectivity to the thermal sensor
for devices like the Analog Devices ADM1021 which has circuitry for
converting the sense information into temperature degrees. The Winbond
chip's external temperature lines may be compatible with the P2 temperature
lines as well.
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 will be the first Intel processor to include the SMBus
The P2 Xeon was the first Intel processor to include the SMBus
interface on the P2 Xeon SEC.
@@ -185,51 +219,92 @@ 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 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.
It is strongly suggested you read doc/modules, and follow the
installation described there. It will allow you to use simple modprobe
commands to load the modules, instead of the more low-level insmod calls.
This file also describes how you can load the modules automatically at
boot-time.
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?
By now, chip detection is fairly good. That means that it is
relatively harmless to insert more chip drivers than you need. This approach
can still lead to problems, though.
In the past, you had to muddle your way through and just tried
several drivers. But starting with 2.3.0, we have an excellent program
that scans all your hardware. It is called 'sensors-detect' and is
installed when you call 'make install'. Just execute this script, and
it will tell you exactly what you want to know.
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. Check the manufacturer's website.
The Motherboard Monitor website (see useful_addresses.html) has a good
cross-reference.
3.3 Which modules should I insert?
You need one module for each adapter you own; if there are
chips on the ISA bus, this includes i2c-isa.o. Also, you need one module
'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 line:
modprobe i2c-isa && modprobe i2c-piix4 && \
modprobe lm78 && modprobe lm75 && modprobe i2c-dev
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?
3.4 Do I need the sensors.conf configuration file?
Usually, you do. It tells how to translate the values the chip
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
@@ -238,6 +313,7 @@ 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
@@ -246,15 +322,17 @@ how you installed, they should be under either /usr/local/include or
3.7 It still does not compile or patch!
Have you installed a recent version of the i2c package? Remember,
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 Problems
----------
4.1 Why do my fans report exactly half/double their values by your code
compared to the BIOS?
@@ -287,8 +365,10 @@ 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 usually the same as Vcore on motherboards which
only support one processor. It is possible, though, that is monitors something
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.
@@ -296,12 +376,21 @@ different.
4.4 How do those ALARMS work? The current value is within range but there
is still an ALARM warning!
An ALARM will go off when a minimum or maximum limit is crossed. It
will stay there until the next internal update - which will be the next time
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. After that, it will only stay if the current value is out of range,
though this too depends a bit on the kind of chip. See the specific chip
documentation in doc/chips for more information.
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
@@ -330,8 +419,8 @@ more information.
4.7 What are VID lines?
These describe the voltage your processors use. This is only supported
for Pentium 2 and newer processors, and even then they are not always
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.
@@ -345,7 +434,7 @@ time to update them. So we only update our readings once each 1.5 seconds
at all).
4.9 It sometimes seems to take a fraction of a seconds before I see the
4.9 It sometimes seems to take a fraction of a second before I see the
sensor reading results. Why?
ISA bus access is fast, but SMBus access is really slow. If you have
@@ -408,27 +497,31 @@ the provided 'sensors' program) instead.
4.14 How do I set new limits?
This is a bit intricate right now. In the near future, this can be
done through the 'sensors' program, which will take account of the
computations specified in the configuration file. At this moment, you must
also put the 'set' commands into the configuration file. This will get
easier in newer versions.
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 will partially solved in the future,
but it is really tough. Double detections can be caused by two things:
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 insmod parameters it suggests.
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. There are some mainboards
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.
@@ -436,47 +529,160 @@ 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.
5 How to ask for help:
4.17 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.
4.18 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.
4.19 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?
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 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.
4.24 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.
4.25 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.x
We don't know the exact cause.
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. Especially, do not mail
Alexander Larsson, as he has left the development team. You can be assured
that any mail sent to sensors@stimpy.netroedge.com will arrive at anyone
who answered your email, so please do not CC: him again.
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:
5.1 What to do if it won't insert?
- 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
Always inspect the output of 'dmesg' and send it to us. Check
/proc/pci for your SMBus adapter, and send the output too. Check whether
you actually have a sensor chip - sometimes, it is only an upgrade option.
If your mainboard manual happens to mention the chip type, send it too.
Tell us what mainboard you own.
5.1 What to do if a module won't insert?
Did you use 'modprobe' instead of 'insmod'??? Don't use insmod.
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.
5.2 What to do if it inserts, but nothing happens?
Check /proc/pci to see whether you have a supported adapter. If it
is not there, we do not support it. Future version may do it. If you want,
you can send us an email telling you have a such-and-so mainboard, together
with the PCI output - that way, we can see what SMBus hosts are used most.
For an ISA sensor chip, did you 'modprobe i2c-isa'? It must be inserted.
For an I2C sensor chip, did you '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, please send us
the usual information (see 5.1).
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 of 'dmesg', /proc/sensors and /proc/pci.
Again, send the output listed above.
5.5 What if it just works like a charm?
@@ -485,7 +691,10 @@ the usual information (see 5.1).
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?
@@ -536,7 +745,9 @@ but until somebody contacts Dell about this and tells us the results, we
can not be sure.
-----------
---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
Rev 2.3 (MDS) General update, 20010121
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