RM23712 TPS
47
fan speeds for different fans based on increasing/decreasing temperatures in different thermal
zones within the chassis.
In the event that system temperatures should continue to increase with the system fans operating at
their maximum speed, platform management may begin to throttle bandwidth of either the memory
subsystem or the processors or both, in order to keep components from overheating and keep the
system operational. Throttling of these subsystems will continue until system temperatures are
reduced below preprogrammed limits.
The power supply will be protected against over temperature conditions caused by excessive
ambient temperature. In an over-temperature protection condition, the power supply module
will shut down.
4.2.1 Fan Speed Control
The baseboard management controller (BMC) supports monitoring and control of fan speed (RPM).
Each fan is associated with a fan speed sensor that detects fan failure.
The system fans are divided into fan domains, each of which has a separate fan speed control
signal and a separate configurable fan control policy. A fan domain can have a set of temperature
and fan sensors associated with it. These are used to determine the current fan domain state.
4.2.2 Programmable Fan PWM Offset
The system provides a BIOS Setup option to boost the system fan speed by a programmable
positive offset or a “Max” setting. Setting the programmable offset causes the BMC to add the offset
to the fan speeds to which it would otherwise be driving the fans. The Max setting causes the BMC
to replace the domain minimum speed with alternate domain minimums that also are programmable
through SDRs.
This capability is offered to provide system administrators the option to manually configure fan
speeds in instances where the fan speed optimized for a given platform may not be sufficient when
a high end add-in adapter is configured into the system. This enables easier usage of the fan speed
control to support Intel as well as third party chassis and better support of ambient temperatures
higher than 35°C.
4.2.3 Hot-Swap Fans
Hot-swap fans are supported. These fans can be removed and replaced while the system is
powered on and operating. The BMC implements fan presence sensors for each hot-swappable
fan.
When a fan is not present, the associated fan speed sensor is put into the reading/unavailable state,
and any associated fan domains are put into the boost state. The fans may already be boosted due
to a previous fan failure or fan removal.
When a removed fan is inserted, the associated fan speed sensor is rearmed. If there are no other
critical conditions causing a fan boost condition, the fan speed returns to the nominal state. Power
cycling or resetting the system re-arms the fan speed sensors and clears fan failure conditions. If
the failure condition is still present, the boost state returns once the sensor has re-initialized and the
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