The entPhysicalIndex of the physical entity for which
the statistics in this entry are maintained.
The physical entity can be a CPU chip, a group of CPUs,
a CPU card etc. The exact type of this entity is described
by its entPhysicalVendorType value. If the CPU statistics
in this entry correspond to more than one physical entity
(or to no physical entity), or if the entPhysicalTable is
not supported on the SNMP agent, the value of this object
must be zero.