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DESCRIPTION

The driver supports an arbitrary set of sensors, provides descriptions regarding what each sensor is used for, and reports whether each sensor is within the specifications as defined by the motherboard manufacturer through ACPI.

The aibs driver supports envsys(4) sensor states as follows:

• Voltage sensors can have a state of ‘valid’, ‘critunder’, or ‘critover’; temperature sensors can have a state of ‘valid’, ‘warnover’, ‘critover’, or ‘invalid’; and fan sensors can have a state of ‘valid’, ‘warnunder’, or ‘warnover’.
• Temperature sensors that have a reading of 0 are marked ‘invalid’, whereas all other sensors are always assumed valid.
• Voltage sensors have a lower and an upper limit, ‘critunder’ and ‘critover’, temperature sensors have two upper limits, ‘warnover’ and ‘critover’, whereas fan sensors may either have only the lower limit ‘warnunder’, or, depending on the vendor's ACPI implementation, one lower and one upper limit, ‘warnunder’ and ‘warnover’.

Sensor values and limits are made available through the envsys(4) interface, and can be monitored with envstat(8). For example, on an ASUS V3-P5G965 barebone:

$ envstat -d aibs0
                     Current  CritMax  WarnMax  WarnMin  CritMin Unit
    Vcore Voltage:     1.152    1.600                      0.850    V
     +3.3 Voltage:     3.312    3.630                      2.970    V
       +5 Voltage:     5.017    5.500                      4.500    V
      +12 Voltage:    12.302   13.800                     10.200    V
  CPU Temperature:    27.000   95.000   80.000                   degC
   MB Temperature:    58.000   95.000   60.000                   degC
    CPU FAN Speed:       878              7200      600           RPM
CHASSIS FAN Speed:         0              7200      700           RPM

Generally, sensors provided by the aibs driver may also be supported by a variety of other drivers, such as lm(4) or itesio(4). The precise collection of aibs sensors is comprised of the sensors specifically utilised in the motherboard design, which may be supported through a combination of one or more physical hardware monitoring chips.

The aibs driver, however, provides the following advantages when compared to the native hardware monitoring drivers:

• Sensor values from aibs are expected to be more reliable. For example, voltage sensors in many hardware monitoring chips can only sense voltage from 0 to 2 or 4 volts, and the excessive voltage is removed by the resistors, which may vary with the motherboard and with the voltage that is being sensed. In aibs, the required resistor factors are provided by the motherboard manufacturer through ACPI; in the native drivers, the resistor factors are encoded into the driver based on the chip manufacturer's recommendations. In essence, sensor values from aibs are very likely to be identical to the readings from the Hardware Monitor screen in the BIOS.
• Sensor descriptions from aibs are more likely to match the markings on the motherboard.
• Sensor states are supported by aibs. The state is reported based on the acceptable range of values for each individual sensor as suggested by the motherboard manufacturer. For example, the threshold for the CPU temperature sensor is likely to be significantly higher than that for the chassis temperature sensor.
• Support for newer chips in aibs. Newer chips may miss a native driver, but should be supported through aibs regardless.

As a result, sensor readings from the actual native hardware monitoring drivers are redundant when aibs is present, and may be ignored as appropriate. Whereas on some supported operating systems the native drivers may have to be specifically disabled should their presence be judged unnecessary, on others the drivers like lm(4) are not probed provided that acpi(4) is configured and the system potentially supports the hardware monitoring chip through ACPI.