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7f15b664 M |
1 | Kernel driver lm78 |
2 | ================== | |
3 | ||
4 | Supported chips: | |
b04f2f7d | 5 | |
27fe048e | 6 | * National Semiconductor LM78 / LM78-J |
b04f2f7d | 7 | |
7f15b664 | 8 | Prefix: 'lm78' |
b04f2f7d | 9 | |
6722fead | 10 | Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports) |
b04f2f7d | 11 | |
7f15b664 | 12 | Datasheet: Publicly available at the National Semiconductor website |
b04f2f7d MCC |
13 | |
14 | http://www.national.com/ | |
15 | ||
7f15b664 | 16 | * National Semiconductor LM79 |
b04f2f7d | 17 | |
7f15b664 | 18 | Prefix: 'lm79' |
b04f2f7d | 19 | |
6722fead | 20 | Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports) |
b04f2f7d | 21 | |
7f15b664 | 22 | Datasheet: Publicly available at the National Semiconductor website |
7f15b664 | 23 | |
b04f2f7d MCC |
24 | http://www.national.com/ |
25 | ||
26 | ||
27 | Authors: | |
28 | - Frodo Looijaard <frodol@dds.nl> | |
29 | - Jean Delvare <jdelvare@suse.de> | |
7f15b664 M |
30 | |
31 | Description | |
32 | ----------- | |
33 | ||
34 | This driver implements support for the National Semiconductor LM78, LM78-J | |
35 | and LM79. They are described as 'Microprocessor System Hardware Monitors'. | |
36 | ||
37 | There is almost no difference between the three supported chips. Functionally, | |
38 | the LM78 and LM78-J are exactly identical. The LM79 has one more VID line, | |
39 | which is used to report the lower voltages newer Pentium processors use. | |
40 | From here on, LM7* means either of these three types. | |
41 | ||
42 | The LM7* implements one temperature sensor, three fan rotation speed sensors, | |
43 | seven voltage sensors, VID lines, alarms, and some miscellaneous stuff. | |
44 | ||
45 | Temperatures are measured in degrees Celsius. An alarm is triggered once | |
46 | when the Overtemperature Shutdown limit is crossed; it is triggered again | |
47 | as soon as it drops below the Hysteresis value. A more useful behavior | |
48 | can be found by setting the Hysteresis value to +127 degrees Celsius; in | |
49 | this case, alarms are issued during all the time when the actual temperature | |
50 | is above the Overtemperature Shutdown value. Measurements are guaranteed | |
51 | between -55 and +125 degrees, with a resolution of 1 degree. | |
52 | ||
53 | Fan rotation speeds are reported in RPM (rotations per minute). An alarm is | |
54 | triggered if the rotation speed has dropped below a programmable limit. Fan | |
55 | readings can be divided by a programmable divider (1, 2, 4 or 8) to give | |
56 | the readings more range or accuracy. Not all RPM values can accurately be | |
57 | represented, so some rounding is done. With a divider of 2, the lowest | |
58 | representable value is around 2600 RPM. | |
59 | ||
60 | Voltage sensors (also known as IN sensors) report their values in volts. | |
61 | An alarm is triggered if the voltage has crossed a programmable minimum | |
62 | or maximum limit. Note that minimum in this case always means 'closest to | |
63 | zero'; this is important for negative voltage measurements. All voltage | |
64 | inputs can measure voltages between 0 and 4.08 volts, with a resolution | |
65 | of 0.016 volt. | |
66 | ||
67 | The VID lines encode the core voltage value: the voltage level your processor | |
68 | should work with. This is hardcoded by the mainboard and/or processor itself. | |
69 | It is a value in volts. When it is unconnected, you will often find the | |
70 | value 3.50 V here. | |
71 | ||
7f15b664 M |
72 | If an alarm triggers, it will remain triggered until the hardware register |
73 | is read at least once. This means that the cause for the alarm may | |
74 | already have disappeared! Note that in the current implementation, all | |
75 | hardware registers are read whenever any data is read (unless it is less | |
76 | than 1.5 seconds since the last update). This means that you can easily | |
77 | miss once-only alarms. | |
78 | ||
79 | The LM7* only updates its values each 1.5 seconds; reading it more often | |
80 | will do no harm, but will return 'old' values. |