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Intel
®
NetStructure
TM
ZT 7102 Chassis Management Module
Power Supplies
Technical Product Specification 83
13.0 Power Supplies
13.1 Power Supply Detection
Unlike blades, there is no hardware support for the detection of power supply presence. Therefore,
an additional process is used to periodically scan for the presence of IPMI power supplies.
Specifically, every five seconds, the process sends an IPMI GetDeviceID to each of the possible
power supply slots. If a response is received, then it is known that an IPMI power supply is present.
13.2 Inhibit, Degrade, and Fail Signals
The CMM and power supplies do share several hardware signals that provide some limited
functionality. These signals work with existing (non-IPMI) power supplies and are expected to
work in the same way for the IPMI power supplies. The Inhibit signal is an output from the CMM
that can be used to effectively turn off a power supply. Querying the Inhibit signal will indicate
whether the CMM has inhibited the supply or not. When a power supply degrades or fails, it
signals these conditions to the CMM using the Degrade and Fail inputs.
The CMM can detect if any power supply is Degraded or Failed, then it can be deduced that there
is a power supply present. The new feature provided by IPMI supplies is the ability to detect the
presence of a power supply when the power supply is operating normally.
13.3 Inhibiting Power Supplies
The CMM has the ability to inhibit any of the power supplies in the chassis. Each power supply can
be inhibited individually.
The state of inhibited power supplies is synchronized from the active to the standby CMM. If a
failover were to occur, the inhibited power supplies would remain inhibited.
The state of inhibited power supplies is not persistent across chassis power cycles.
13.4 Precautions For Inhibiting Power Supplies
Care should be taken when inhibiting power supplies. Inhibiting certain supplies or groups of
supplies may cause the loss of power to portions of the chassis, including power to the CMMs. It is
also possible to inhibit all of the power supplies, which causes a loss of power to the entire chassis,
including the CMMs.
Once the CMMs lose power, they are no longer able to drive the INHIBIT# line to the power
supplies, which causes all of the supplies to power up again. Losing power to both CMMs is
equivalent to power cycling the chassis.
Care should be taken to prevent inhibiting all of the supplies in a chassis as well as losing power to
both CMMs so that the reset condition does not occur.