1Kernel driver lm83
2==================
3
4Supported chips:
5  * National Semiconductor LM83
6    Prefix: 'lm83'
7    Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
8    Datasheet: Publicly available at the National Semiconductor website
9               http://www.national.com/pf/LM/LM83.html
10  * National Semiconductor LM82
11    Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
12    Datasheet: Publicly available at the National Semiconductor website
13               http://www.national.com/pf/LM/LM82.html
14
15
16Author: Jean Delvare <jdelvare@suse.de>
17
18Description
19-----------
20
21The LM83 is a digital temperature sensor. It senses its own temperature as
22well as the temperature of up to three external diodes. The LM82 is
23a stripped down version of the LM83 that only supports one external diode.
24Both are compatible with many other devices such as the LM84 and all
25other ADM1021 clones. The main difference between the LM83 and the LM84
26in that the later can only sense the temperature of one external diode.
27
28Using the adm1021 driver for a LM83 should work, but only two temperatures
29will be reported instead of four.
30
31The LM83 is only found on a handful of motherboards. Both a confirmed
32list and an unconfirmed list follow. If you can confirm or infirm the
33fact that any of these motherboards do actually have an LM83, please
34contact us. Note that the LM90 can easily be misdetected as a LM83.
35
36Confirmed motherboards:
37    SBS         P014
38    SBS         PSL09
39
40Unconfirmed motherboards:
41    Gigabyte    GA-8IK1100
42    Iwill       MPX2
43    Soltek      SL-75DRV5
44
45The LM82 is confirmed to have been found on most AMD Geode reference
46designs and test platforms.
47
48The driver has been successfully tested by Magnus Forsström, who I'd
49like to thank here. More testers will be of course welcome.
50
51The fact that the LM83 is only scarcely used can be easily explained.
52Most motherboards come with more than just temperature sensors for
53health monitoring. They also have voltage and fan rotation speed
54sensors. This means that temperature-only chips are usually used as
55secondary chips coupled with another chip such as an IT8705F or similar
56chip, which provides more features. Since systems usually need three
57temperature sensors (motherboard, processor, power supply) and primary
58chips provide some temperature sensors, the secondary chip, if needed,
59won't have to handle more than two temperatures. Thus, ADM1021 clones
60are sufficient, and there is no need for a four temperatures sensor
61chip such as the LM83. The only case where using an LM83 would make
62sense is on SMP systems, such as the above-mentioned Iwill MPX2,
63because you want an additional temperature sensor for each additional
64CPU.
65
66On the SBS P014, this is different, since the LM83 is the only hardware
67monitoring chipset. One temperature sensor is used for the motherboard
68(actually measuring the LM83's own temperature), one is used for the
69CPU. The two other sensors must be used to measure the temperature of
70two other points of the motherboard. We suspect these points to be the
71north and south bridges, but this couldn't be confirmed.
72
73All temperature values are given in degrees Celsius. Local temperature
74is given within a range of 0 to +85 degrees. Remote temperatures are
75given within a range of 0 to +125 degrees. Resolution is 1.0 degree,
76accuracy is guaranteed to 3.0 degrees (see the datasheet for more
77details).
78
79Each sensor has its own high limit, but the critical limit is common to
80all four sensors. There is no hysteresis mechanism as found on most
81recent temperature sensors.
82
83The lm83 driver will not update its values more frequently than every
84other second; reading them more often will do no harm, but will return
85'old' values.
86