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diff --git a/Documentation/hwmon/lm83.rst b/Documentation/hwmon/lm83.rst new file mode 100644 index 000000000000..ecf83819960e --- /dev/null +++ b/Documentation/hwmon/lm83.rst @@ -0,0 +1,97 @@ +Kernel driver lm83 +================== + +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 <jdelvare@suse.de> + +Description +----------- + +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. |