Specifications

QSSC-S4R Technical Product Specification Processor Presence and Population Check
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The BMC provides 10-bit A/Ds for voltage monitoring. The BMC FW reads this 10- bit value and scales it to fit into the
1-byte data field supported by IPMI. The BMC knows what scale factor to use by retrieving it from an OEM SDR which
provides a scale factor for each voltage sensor in the system.
The BMC firmware computes the sensor value as follows:
SensorValue = (A/D10-Bit reading * ScaleFactor) / 10000
BMC also uses external SMBUS devices to monitor CPU voltages sensors.
24.13 Standard Fan Management
The BMC controls and monitors the system fans. Each fan is associated with a fan speed sensor that detects fan
failure and may also be associated with a fan presence sensor for hot-swap support. For redundant fan configurations,
the fan failure and presence status determines the fan redundancy sensor state.
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.
A fan domain has four states: sleep, nominal, and lower boost and boost. The sleep lower boost and boost states have
fixed (but configurable via OEM SDRs) fan speeds associated with them. The nominal state has a variable speed
determined by the fan domain policy. See Section 24.13.4. An OEM SDR record is used to configure the fan domain
policy. See the descriptions of the TControl Fan Speed Control Record formats in Appendix A. The Set SM Signal
command can be used to manually force the fan domain speed to a selected value, overriding any other control or
policy.
The fan domain state is controlled by several factors. In order of precedence, high to low:
x Boost
x Associated fan in a critical state or missing. The SDR describes which fan domains are boosted in response to
a fan failure or removal in each domain.
x Any fan has failed, as indicated by its fan tach sensor reading crossing a lower critical threshold.
x Any fan is removed.
x The BMC is in firmware update mode, or the operational firmware is corrupted.
x If any of the above conditions apply, the fans are set to a fixed boost state speed.
x Lower Boost
x Any system temperature sensor reading has crossed an upper critical threshold (Power supply temperature
sensors do not contribute to this boosting)
x Chassis intrusion is active
x Sleep
x No boost conditions, the system is in ACPI S1 sleep state. Fan speed control is determined by the available
SDRs. Fans may be set to a fixed state, or basic fan management can be applied.
x Nominal
x See Section 24.13.4.
The fan control SDRs provide a means to set 2 different boost values for a specific fan domain (Lower Boost and
Boost). One applies for fan failure or missing conditions. The other applies for critical temperature and chassis intrusion
conditions. If more than one condition is simultaneously present, then the higher boost value is applied.
24.13.1 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 (sensor type = Slot / Connector (21h), event / reading type = Sensor
Specific (6Fh)) for each hot swappable fan.
When a fan is not present, the associated fan speed sensor is put into the reading/state 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 rearms