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4.3.6 Thermal Sensor Input to Fan Speed Control
The BMC uses various IPMI sensors as input to the fan speed control. Some of the sensors are IPMI
models of actual physical sensors,
whereas some are “virtual” sensors whose values are derived from
physical sensors using calculations and/or tabular information.
The following IPMI thermal sensors are used as input to the fan speed control:
Front Panel Temperature Sensor1
Baseboard Temperature Sensor2
CPU Margin Sensors3, 5, 6
DIMM Thermal Margin Sensors3, 5
Exit Air Temperature Sensor1, 4, 8
Intel® C600 chipset Temperature Sensor4, 6
On-board Ethernet Controller Temperature Sensors4, 6
Add-In Intel® SAS/IO Module Temperature Sensors4, 6
PSU Thermal Sensor4, 9
CPU VR Temperature Sensors4, 7
DIMM VR Temperature Sensors4, 7
Integrated BMC Temperature Sensor4, 7
Global Aggregate Thermal Margin Sensors3, 8
Note:
1. For fan speed control in Intel® chassis
2. For fan speed control in third party chassis
3. Temperature margin from throttling threshold
4. Absolute temperature
5. PECI value
6. On-die sensor
7. On-board sensor
8. Virtual sensor
9. Available only when PSU has PMBus*
The simple model shown in the following figure is a high level graphic explaining how the fan speed
control structure creates the resulting fan speeds.