1Kernel driver lm83
2==================
3
4Supported chips:
5
6  * National Semiconductor LM83
7
8    Prefix: 'lm83'
9
10    Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
11
12    Datasheet: Publicly available at the National Semiconductor website
13
14	       http://www.national.com/pf/LM/LM83.html
15
16  * National Semiconductor LM82
17
18    Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
19
20    Datasheet: Publicly available at the National Semiconductor website
21
22	       http://www.national.com/pf/LM/LM82.html
23
24Author: Jean Delvare <jdelvare@suse.de>
25
26Description
27-----------
28
29The LM83 is a digital temperature sensor. It senses its own temperature as
30well as the temperature of up to three external diodes. The LM82 is
31a stripped down version of the LM83 that only supports one external diode.
32Both are compatible with many other devices such as the LM84 and all
33other ADM1021 clones. The main difference between the LM83 and the LM84
34in that the later can only sense the temperature of one external diode.
35
36Using the adm1021 driver for a LM83 should work, but only two temperatures
37will be reported instead of four.
38
39The LM83 is only found on a handful of motherboards. Both a confirmed
40list and an unconfirmed list follow. If you can confirm or infirm the
41fact that any of these motherboards do actually have an LM83, please
42contact us. Note that the LM90 can easily be misdetected as a LM83.
43
44Confirmed motherboards:
45    ===		=====
46    SBS         P014
47    SBS         PSL09
48    ===		=====
49
50Unconfirmed motherboards:
51    =========== ==========
52    Gigabyte    GA-8IK1100
53    Iwill       MPX2
54    Soltek      SL-75DRV5
55    =========== ==========
56
57The LM82 is confirmed to have been found on most AMD Geode reference
58designs and test platforms.
59
60The driver has been successfully tested by Magnus Forsstr��m, who I'd
61like to thank here. More testers will be of course welcome.
62
63The fact that the LM83 is only scarcely used can be easily explained.
64Most motherboards come with more than just temperature sensors for
65health monitoring. They also have voltage and fan rotation speed
66sensors. This means that temperature-only chips are usually used as
67secondary chips coupled with another chip such as an IT8705F or similar
68chip, which provides more features. Since systems usually need three
69temperature sensors (motherboard, processor, power supply) and primary
70chips provide some temperature sensors, the secondary chip, if needed,
71won't have to handle more than two temperatures. Thus, ADM1021 clones
72are sufficient, and there is no need for a four temperatures sensor
73chip such as the LM83. The only case where using an LM83 would make
74sense is on SMP systems, such as the above-mentioned Iwill MPX2,
75because you want an additional temperature sensor for each additional
76CPU.
77
78On the SBS P014, this is different, since the LM83 is the only hardware
79monitoring chipset. One temperature sensor is used for the motherboard
80(actually measuring the LM83's own temperature), one is used for the
81CPU. The two other sensors must be used to measure the temperature of
82two other points of the motherboard. We suspect these points to be the
83north and south bridges, but this couldn't be confirmed.
84
85All temperature values are given in degrees Celsius. Local temperature
86is given within a range of 0 to +85 degrees. Remote temperatures are
87given within a range of 0 to +125 degrees. Resolution is 1.0 degree,
88accuracy is guaranteed to 3.0 degrees (see the datasheet for more
89details).
90
91Each sensor has its own high limit, but the critical limit is common to
92all four sensors. There is no hysteresis mechanism as found on most
93recent temperature sensors.
94
95The lm83 driver will not update its values more frequently than every
96other second; reading them more often will do no harm, but will return
97'old' values.
98