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