Ipmi 'Sensor Model - Intel SE7520JR2 Technical Manual

Intel® Server Board SE7520JR2 Platform Management
5.1.3

IPMI 'Sensor Model'

An IPMI-compatible 'Sensor Model' is used to unify the way that temperature, voltage, and other
platform management status and control is represented and accessed. The implementation of
this model is done according to command and data formats defined in the Intelligent Platform
Management Interface Specification.
The majority of monitored platform elements are accessed as logical 'Sensors' under this
model. This access is accomplished using an abstracted, message-based interface (IPMI
messages). Instead of having system software access the platform monitoring and control
hardware registers directly, it sends commands, such as the Get Sensor Reading command, for
sensor access. The message-based interface isolates software from the particular hardware
implementation.
System Management Software discovers the platform's sensor capabilities by reading the
Sensor Data Records from a Sensor Data Record Repository managed by the management
controller. Sensor Data Records provide a list of the sensors, their characteristics, location,
type, and associated Sensor Number, for sensors in a particular system. The Sensor Data
Records also hold default threshold values (if the sensor has threshold based events), factors
for converting a sensor reading into the appropriate units (mV, rpm, degrees Celsius, etc.), and
information on the types of events that a sensor can generate.
Sensor Data Records also provide information on where Field Replaceable Unit (FRU)
information is located, and information to link sensors with the entity and/or FRU they're
associated with.
Information in the SDRs is also used for configuring and restoring sensor thresholds and event
generation whenever the system powers up or is reset. This is accomplished via a process
called the 'initialization agent'. The BMC reads the SDRs and based on bit settings, writes the
threshold data. Then it enables event generation for the various sensors it monitors and in
management controllers on the IPMB for systems based on the Standard or Advanced
management models.
System Management Software uses the data contained in the Sensor Data Record information
to locate sensors in order to poll them, interpret, and present their data readings, adjust
thresholds, interpret SEL entries, and alter event generation settings.
In Professional and Advanced management models, SDRs also provide a mechanism for
extending the baseboard management with additional chassis or OEM 'value-added' monitoring
and events. The baseboard monitoring can be extended by implementing an IPMI-compatible
management controller, connecting it to the IPMB, and adding new SDRs describing that
controller and its sensors to the SDR Repository. System Management Software can then read
the SDRs and use them to automatically incorporate the additional sensors.
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