This file documents the lm78 directories.

There will be one directory created for each detected LM78, LM78-J or LM79
chip. Each chip can both be on the ISA bus and the SMBus. Directories
are called things like lm78-isa-0290, lm78-j-i2c-3-4e or lm79-isa-0280.
/proc/sys/dev/sensors/chips contains the SYSCTL values for all chip
directories.

Within each LM78 directory, you can find the following files:
* alarms (LM78_SYSCTL_ALARMS)
  A number which indicates which alarms are on. An alarm gets triggered when
  some limit has been crossed. Even if the cause of the alarm is over, it
  stays triggered until it has been read at least once. Because the LM78
  values are updated at most once every 1.5 seconds, this means the alarm
  can be read several times before it is erased.
  This file can not be written to.
  The number is the logical OR of the following components:
  - LM78_ALARM_IN[0-6]
    Gets triggered when the corresponding in value is higher or lower than
    its limits
  - LM78_ALARM_FAN[1-3]
    Gets triggered when the corresponding fan value is lower than its limit
  - LM78_ALARM_TEMP
    Gets triggered when the temp value has crossed its limits. See the 
    description under temp.
  - LM78_ALARM_BTI
    Gets triggered if some other chip which is connected to it has crossed
    its limits. Usually, it is connected to all LM75 chips; if at least one
    crosses its limits, this bit gets set.
  - LM78_ALARM_CHAS
    Gets triggered if someone opens your computer case (if connected at all).
  - LM78_ALARM_FIFO
    Gets triggered if something is very wrong with our LM78 driver. Ignore.
  - LM78_ALARM_SMI_IN
    Gets triggered if some other chip has triggered a SMI interrupt. Can be
    ignored.
  If accessed through sysctl, this value is a long.
* fan[1-3] (LM78_SYSCTL_FAN[1-3])
  A list of two numbers. The first is the minimum fan rotation limit; the
  second is the current fan rotation speed. Both are in RPM (rotation per
  minute). An alarm is triggered if the rotation speed drops below the
  limit. The first value can be changed. Not all RPM values can accurately
  be represented, so some rounding is done.
  If accessed through sysctl, this is a list of longs.
* fan_div (LM78_SYSCTL_FAN_DIV)
  A list of three numbers, one for each fan. Each number can be either 1, 2,
  4 or 8. It is the internal scaling factor used for the FAN rotations. If
  you change this number, the FAN readings get more or less detailed, but
  the range in which they can be read too. Higher numbers give better 
  resolution, but less range. The first two numbers can be changed, the
  third not.
  If accessed through sysctl, this is a list of longs.
* in[0-6] (LM78_SYSCTL_IN[0-6])
  A list of three numbers. The first is the minimum limit, the second is the
  maximum limit, and the third is the current value. If you have a weird
  mainboard, all values may be off because some other scaling factor has
  to be used; user-space programs should compensate for this. Note that
  minimum means 'closest to zero'; so if the normal value equals -10, a
  minimum could equal -9, and a maximum -11. IN0 and IN1 reflect core
  voltages; they are by default set from the vid values, or set to 2.80V
  if the vid lines seem to be unconnected. IN2 should equal +3.30V,
  IN3 +5.00V, IN4 +12.00V, IN5 -12.00V and IN6 -5V. Not all voltage values
  can be accurately represented, so some rounding is done.
  The first two numbers can be changed, the third not.
  If accessed through sysctl, this is a list of longs, each being the voltage
  times 100.
* temp
  A list of three numbers. The first number is the Overtemperature Shutdown
  value; the second is the Hysteris value and the third number is the
  current value. The first two values can be modified. All values are in
  degrees Celcius. An alarm is issued when the temperature first gets above
  the Overtemperature Shutdown value; no more alarms are issued until the
  temperature gets below the Hysteris value, at which moment another alarm
  is issued, and the state is reset. A more useful behaviour can be found
  by setting the Hysteris value to +127 degrees Celcius; in this case, 
  alarms are issued during all the time when the actual temperature is 
  above the Overtemperature Shutdown value.
  The first two numbers can be changed, the third not.
  If accessed through sysctl, this is a list of longs, each being the
  temperature in degrees Celcius times 10.
* vid
  The core voltage value (the voltage level your processor should work with),
  in volts. This is the value IN0 and IN1 are initialized to. If unconnected,
  it usually reads 3.50V.
  This number can not be changed.
  If accessed through sysctl, this is a long, being the voltage times 100.

The data for each LM78 is updated each 1.5 seconds, but only if it is actually
read.