Setting up the Environmental Monitoring 

Configure->LM79

Environmental Monitoring is the name given to the ability of your Server to monitor the state of some of its hardware components, e.g. the speed of the fans, the internal temperature and the voltages coming out the power supply. This is done by a chip such as the LM79. Unfortunately, the readings that come directly from this device are in the range 0 to 255, which means they must be interpreted before they become meaningful.

With the voltage readings the circuit board designers usually try to get the correct reading to come out to around 150-200. You should always have a +5v, +12v, -12v & -5v and they are almost always measured one after the other in that order. The +/-12v are allowed to vary by at least 10% either way, but the +/-5v should always be within 5% either way. To get the correct reading you must set a scaling factor in the factor column appropriate for that input. Readings taken from voltage rails between 0 and 4v will usually have a 'factor' of 0.016 as these voltages can be connected directly into the LM79.

With the fan speed, the measurement normally represents the time it takes to make a half revolution, although there are fans that provide only one or as many as four timing pulses per revolution or (the normal divisor is 2, but divisors of 1,4 or 8 can be applied). This scheme also means that the fan speed is inversely proportional to the reading taken, hence a tick box ("1/x") is provided to compensate. The last three reading from an LM79 are the fan speeds.

The temperature is usually measured directly in degrees Centigrade, so only needs a factor applied if you prefer Fahrenheit (or Kelvin).

Setting up the scaling
If your system is supported by one of the templates, you should simply import its values and use them.  If your system is not supported directly, you can configure the operation as follows.

If you go into the BIOS configuration pages you should find the calculated readings from the environmental monitoring chip on the "Chipset Features" page. This will help you determine the order in which the readings are taken and their "factors", which will vary from one motherboard design to another.

The "factor" for the Fan Speed should always relate to a base value of 1,350,000 which may be divided by an integer, usually 2, 4 or 8 (the 'normal' value is 675,000). The reading from the LM79 is then divided into the factor to give the fan speed. e.g. with a factor of 675,000, a reading of 150 would represent a fan speed of 4500. To see the "actual" readings that are coming off the LM79 chip, set all factors to one and untick all "1/x" boxes.

The option "1/x" tells your Server whether the LM79 reading is inversely proportional to the display value or not. This is ever only true for the fan speeds.
 
If "1/x" is ticked: <display value> = <factor> / <reading>
If "1/x" is not ticked: <display value> = <factor> * <reading>

The "0.xx" option should be ticked if you want the display value to show two decimal places, otherwise just the integer value is displayed. The Max and Min values set the range of readings which is considered to be normal.  If the reading is outside this range, the blue tick  is changed to a red cross . The "?" tick box defines whether that reading is supported on your motherboard or not. For example, one of the three fan speeds is generally reserved for a second CPU, which many motherboards do not support.