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