| 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 <khali@linux-fr.org> |
| |
| 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 Forsstrรถm, 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. |
