linux/Documentation/hwmon/lm83
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   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 <khali@linux-fr.org>
  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
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