Intel® Server Board X38ML
Platform Management
Revision 1.3
Intel order number E15331-006
71
OEM SDR records are used to configure which temperature sensors are associated with which
fan control domains and the algorithmic relationship between the temperature and fan speed.
Multiple OEM SDRs can reference or control the same fan control domain, and multiple OEM
SDRs can reference the same temperature sensors.
The PWM duty-cycle value for a domain is computed as a percentage using one or more
instances of a stepwise linear algorithm and a clamp algorithm. The transition from one
computed nominal fan speed (PWM value) to another is ramped over time to minimize audible
transitions. The ramp rate is configurable via the OEM SDR.
You can define multiple stepwise linear and clamp controls for each fan domain and used
simultaneously. For each domain, the BMC uses the maximum of the domain’s stepwise linear
control contributions and the sum of the domain’s clamp control contributions to compute the
domain’s PWM value, except you can configure a stepwise linear instance to provide the
domain maximum.
Hysteresis can be specified to minimize fan speed oscillation and to smooth fan speed
transitions. If a legacy Tcontrol SDR format does not allow specifying hysteresis, the BMC
assumes a hysteresis value of zero.
5.16.3
Thermal and Acoustic Management
This feature refers to enhanced fan management to keep the system optimally cooled while
reducing the amount of noise generated by the system fans. Aggressive acoustics standards
might require a trade-off between fan speed and system performance parameters that
contribute to the cooling requirements, primarily memory bandwidth. The BIOS, BMC, and
SDRs work together to control and determine the trade-off.
5.17
Power Unit Management
The BMC supports an IPMI type 09h, or power unit sensor, using the following offsets:
Event Offset Trigger
Meaning
00h Power
off
04h AC
lost
05h
Soft power control failure
5.17.1
Power Off
The BMC asserts the
Power Off
offset whenever the system DC power is off.
5.17.2
AC Lost
The BMC asserts the
AC lost
offset when AC power is applied to the system and the previous
system power state was on. This offset is used for event generation only and does not remain
asserted.
5.17.3
Soft Power Control Fault
The BMC asserts the
Soft Power Control Failure
offset if the system fails to power-on within 8
seconds due to the following power control sources: