lm83.rst (3808B)
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 Forsström, 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.