Based on kernel version 4.0. Page generated on 2015-04-14 21:24 EST.
1 Kernel driver lm78 2 ================== 3 4 Supported chips: 5 * National Semiconductor LM78 / LM78-J 6 Prefix: 'lm78' 7 Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports) 8 Datasheet: Publicly available at the National Semiconductor website 9 http://www.national.com/ 10 * National Semiconductor LM79 11 Prefix: 'lm79' 12 Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports) 13 Datasheet: Publicly available at the National Semiconductor website 14 http://www.national.com/ 15 16 Authors: Frodo Looijaard <firstname.lastname@example.org> 17 Jean Delvare <email@example.com> 18 19 Description 20 ----------- 21 22 This driver implements support for the National Semiconductor LM78, LM78-J 23 and LM79. They are described as 'Microprocessor System Hardware Monitors'. 24 25 There is almost no difference between the three supported chips. Functionally, 26 the LM78 and LM78-J are exactly identical. The LM79 has one more VID line, 27 which is used to report the lower voltages newer Pentium processors use. 28 From here on, LM7* means either of these three types. 29 30 The LM7* implements one temperature sensor, three fan rotation speed sensors, 31 seven voltage sensors, VID lines, alarms, and some miscellaneous stuff. 32 33 Temperatures are measured in degrees Celsius. An alarm is triggered once 34 when the Overtemperature Shutdown limit is crossed; it is triggered again 35 as soon as it drops below the Hysteresis value. A more useful behavior 36 can be found by setting the Hysteresis value to +127 degrees Celsius; in 37 this case, alarms are issued during all the time when the actual temperature 38 is above the Overtemperature Shutdown value. Measurements are guaranteed 39 between -55 and +125 degrees, with a resolution of 1 degree. 40 41 Fan rotation speeds are reported in RPM (rotations per minute). An alarm is 42 triggered if the rotation speed has dropped below a programmable limit. Fan 43 readings can be divided by a programmable divider (1, 2, 4 or 8) to give 44 the readings more range or accuracy. Not all RPM values can accurately be 45 represented, so some rounding is done. With a divider of 2, the lowest 46 representable value is around 2600 RPM. 47 48 Voltage sensors (also known as IN sensors) report their values in volts. 49 An alarm is triggered if the voltage has crossed a programmable minimum 50 or maximum limit. Note that minimum in this case always means 'closest to 51 zero'; this is important for negative voltage measurements. All voltage 52 inputs can measure voltages between 0 and 4.08 volts, with a resolution 53 of 0.016 volt. 54 55 The VID lines encode the core voltage value: the voltage level your processor 56 should work with. This is hardcoded by the mainboard and/or processor itself. 57 It is a value in volts. When it is unconnected, you will often find the 58 value 3.50 V here. 59 60 If an alarm triggers, it will remain triggered until the hardware register 61 is read at least once. This means that the cause for the alarm may 62 already have disappeared! Note that in the current implementation, all 63 hardware registers are read whenever any data is read (unless it is less 64 than 1.5 seconds since the last update). This means that you can easily 65 miss once-only alarms. 66 67 The LM7* only updates its values each 1.5 seconds; reading it more often 68 will do no harm, but will return 'old' values.