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Kernel driver lm83

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Supported chips:

  * National Semiconductor LM83

    Prefix: 'lm83'

    Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e

    Datasheet: Publicly available at the National Semiconductor website

               http://www.national.com/pf/LM/LM83.html

  * National Semiconductor LM82

    Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e

    Datasheet: Publicly available at the National Semiconductor website

               http://www.national.com/pf/LM/LM82.html

Author: Jean Delvare 

Description

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The LM83 is a digital temperature sensor. It senses its own temperature as

well as the temperature of up to three external diodes. The LM82 is

a stripped down version of the LM83 that only supports one external diode.

Both are compatible with many other devices such as the LM84 and all

other ADM1021 clones. The main difference between the LM83 and the LM84

in that the later can only sense the temperature of one external diode.

Using the adm1021 driver for a LM83 should work, but only two temperatures

will be reported instead of four.

The LM83 is only found on a handful of motherboards. Both a confirmed

list and an unconfirmed list follow. If you can confirm or infirm the

fact that any of these motherboards do actually have an LM83, please

contact us. Note that the LM90 can easily be misdetected as a LM83.

Confirmed motherboards:

    SBS         P014

    SBS         PSL09

Unconfirmed motherboards:

    Gigabyte    GA-8IK1100

    Iwill       MPX2

    Soltek      SL-75DRV5

The LM82 is confirmed to have been found on most AMD Geode reference

designs and test platforms.

The driver has been successfully tested by Magnus Forsström, who I'd

like to thank here. More testers will be of course welcome.

The fact that the LM83 is only scarcely used can be easily explained.

Most motherboards come with more than just temperature sensors for

health monitoring. They also have voltage and fan rotation speed

sensors. This means that temperature-only chips are usually used as

secondary chips coupled with another chip such as an IT8705F or similar

chip, which provides more features. Since systems usually need three

temperature sensors (motherboard, processor, power supply) and primary

chips provide some temperature sensors, the secondary chip, if needed,

won't have to handle more than two temperatures. Thus, ADM1021 clones

are sufficient, and there is no need for a four temperatures sensor

chip such as the LM83. The only case where using an LM83 would make

sense is on SMP systems, such as the above-mentioned Iwill MPX2,

because you want an additional temperature sensor for each additional

CPU.

On the SBS P014, this is different, since the LM83 is the only hardware

monitoring chipset. One temperature sensor is used for the motherboard

(actually measuring the LM83's own temperature), one is used for the

CPU. The two other sensors must be used to measure the temperature of

two other points of the motherboard. We suspect these points to be the

north and south bridges, but this couldn't be confirmed.

All temperature values are given in degrees Celsius. Local temperature

is given within a range of 0 to +85 degrees. Remote temperatures are

given within a range of 0 to +125 degrees. Resolution is 1.0 degree,

accuracy is guaranteed to 3.0 degrees (see the datasheet for more

details).

Each sensor has its own high limit, but the critical limit is common to

all four sensors. There is no hysteresis mechanism as found on most

recent temperature sensors.

The lm83 driver will not update its values more frequently than every

other second; reading them more often will do no harm, but will return

'old' values.