0001 Kernel driver lm83
0002 ==================
0003
0004 Supported chips:
0005
0006 * National Semiconductor LM83
0007
0008 Prefix: 'lm83'
0009
0010 Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
0011
0012 Datasheet: Publicly available at the National Semiconductor website
0013
0014 http://www.national.com/pf/LM/LM83.html
0015
0016 * National Semiconductor LM82
0017
0018 Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
0019
0020 Datasheet: Publicly available at the National Semiconductor website
0021
0022 http://www.national.com/pf/LM/LM82.html
0023
0024 Author: Jean Delvare <jdelvare@suse.de>
0025
0026 Description
0027 -----------
0028
0029 The LM83 is a digital temperature sensor. It senses its own temperature as
0030 well as the temperature of up to three external diodes. The LM82 is
0031 a stripped down version of the LM83 that only supports one external diode.
0032 Both are compatible with many other devices such as the LM84 and all
0033 other ADM1021 clones. The main difference between the LM83 and the LM84
0034 in that the later can only sense the temperature of one external diode.
0035
0036 Using the adm1021 driver for a LM83 should work, but only two temperatures
0037 will be reported instead of four.
0038
0039 The LM83 is only found on a handful of motherboards. Both a confirmed
0040 list and an unconfirmed list follow. If you can confirm or infirm the
0041 fact that any of these motherboards do actually have an LM83, please
0042 contact us. Note that the LM90 can easily be misdetected as a LM83.
0043
0044 Confirmed motherboards:
0045 === =====
0046 SBS P014
0047 SBS PSL09
0048 === =====
0049
0050 Unconfirmed motherboards:
0051 =========== ==========
0052 Gigabyte GA-8IK1100
0053 Iwill MPX2
0054 Soltek SL-75DRV5
0055 =========== ==========
0056
0057 The LM82 is confirmed to have been found on most AMD Geode reference
0058 designs and test platforms.
0059
0060 The driver has been successfully tested by Magnus Forsström, who I'd
0061 like to thank here. More testers will be of course welcome.
0062
0063 The fact that the LM83 is only scarcely used can be easily explained.
0064 Most motherboards come with more than just temperature sensors for
0065 health monitoring. They also have voltage and fan rotation speed
0066 sensors. This means that temperature-only chips are usually used as
0067 secondary chips coupled with another chip such as an IT8705F or similar
0068 chip, which provides more features. Since systems usually need three
0069 temperature sensors (motherboard, processor, power supply) and primary
0070 chips provide some temperature sensors, the secondary chip, if needed,
0071 won't have to handle more than two temperatures. Thus, ADM1021 clones
0072 are sufficient, and there is no need for a four temperatures sensor
0073 chip such as the LM83. The only case where using an LM83 would make
0074 sense is on SMP systems, such as the above-mentioned Iwill MPX2,
0075 because you want an additional temperature sensor for each additional
0076 CPU.
0077
0078 On the SBS P014, this is different, since the LM83 is the only hardware
0079 monitoring chipset. One temperature sensor is used for the motherboard
0080 (actually measuring the LM83's own temperature), one is used for the
0081 CPU. The two other sensors must be used to measure the temperature of
0082 two other points of the motherboard. We suspect these points to be the
0083 north and south bridges, but this couldn't be confirmed.
0084
0085 All temperature values are given in degrees Celsius. Local temperature
0086 is given within a range of 0 to +85 degrees. Remote temperatures are
0087 given within a range of 0 to +125 degrees. Resolution is 1.0 degree,
0088 accuracy is guaranteed to 3.0 degrees (see the datasheet for more
0089 details).
0090
0091 Each sensor has its own high limit, but the critical limit is common to
0092 all four sensors. There is no hysteresis mechanism as found on most
0093 recent temperature sensors.
0094
0095 The lm83 driver will not update its values more frequently than every
0096 other second; reading them more often will do no harm, but will return
0097 'old' values.
