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-Kernel driver lm78
-Supported chips:
- * National Semiconductor LM78 / LM78-J
- Prefix: 'lm78'
- Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports)
- Datasheet: Publicly available at the National Semiconductor website
- * National Semiconductor LM79
- Prefix: 'lm79'
- Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports)
- Datasheet: Publicly available at the National Semiconductor website
-Authors: Frodo Looijaard <>
- Jean Delvare <>
-This driver implements support for the National Semiconductor LM78, LM78-J
-and LM79. They are described as 'Microprocessor System Hardware Monitors'.
-There is almost no difference between the three supported chips. Functionally,
-the LM78 and LM78-J are exactly identical. The LM79 has one more VID line,
-which is used to report the lower voltages newer Pentium processors use.
-From here on, LM7* means either of these three types.
-The LM7* implements one temperature sensor, three fan rotation speed sensors,
-seven voltage sensors, VID lines, alarms, and some miscellaneous stuff.
-Temperatures are measured in degrees Celsius. An alarm is triggered once
-when the Overtemperature Shutdown limit is crossed; it is triggered again
-as soon as it drops below the Hysteresis value. A more useful behavior
-can be found by setting the Hysteresis value to +127 degrees Celsius; in
-this case, alarms are issued during all the time when the actual temperature
-is above the Overtemperature Shutdown value. Measurements are guaranteed
-between -55 and +125 degrees, with a resolution of 1 degree.
-Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
-triggered if the rotation speed has dropped below a programmable limit. Fan
-readings can be divided by a programmable divider (1, 2, 4 or 8) to give
-the readings more range or accuracy. Not all RPM values can accurately be
-represented, so some rounding is done. With a divider of 2, the lowest
-representable value is around 2600 RPM.
-Voltage sensors (also known as IN sensors) report their values in volts.
-An alarm is triggered if the voltage has crossed a programmable minimum
-or maximum limit. Note that minimum in this case always means 'closest to
-zero'; this is important for negative voltage measurements. All voltage
-inputs can measure voltages between 0 and 4.08 volts, with a resolution
-of 0.016 volt.
-The VID lines encode the core voltage value: the voltage level your processor
-should work with. This is hardcoded by the mainboard and/or processor itself.
-It is a value in volts. When it is unconnected, you will often find the
-value 3.50 V here.
-If an alarm triggers, it will remain triggered until the hardware register
-is read at least once. This means that the cause for the alarm may
-already have disappeared! Note that in the current implementation, all
-hardware registers are read whenever any data is read (unless it is less
-than 1.5 seconds since the last update). This means that you can easily
-miss once-only alarms.
-The LM7* only updates its values each 1.5 seconds; reading it more often
-will do no harm, but will return 'old' values.