124 IBM Power 750 and 760 Technical Overview and Introduction
On the POWER7+ processors, a partition can be defined with a processor capacity as small
as 0.05 processing units. This number represents 0.05 of a physical processor. Each physical
processor can be shared by up to 20 shared processor partitions, and the partition’s
entitlement can be incremented fractionally by as little as 0.01 of the processor. The shared
processor partitions are dispatched and time-sliced on the physical processors under control
of the POWER Hypervisor. The shared processor partitions are created and managed by
the HMC.
The IBM Power 750 supports up to 32 cores, and has the following maximums:
Up to 32 dedicated partitions
Up to 640 micropartitions (maximum 20 micropartitions per physical active core)
The Power 760 allows up to 48 cores in a single system, supporting the following maximums:
Up to 48 dedicated partitions
Up to 960 micropartitions (maximum 20 micropartitions per physical active core)
An important point is that the maximums stated are supported by the hardware, but the
practical limits depend on application workload demands.
Consider the following additional information about virtual processors:
A virtual processor can be running (dispatched) either on a physical processor or as
standby waiting for a physical processor to became available.
Virtual processors do not introduce any additional abstraction level. They are only a
dispatch entity. When running on a physical processor, virtual processors run at the same
speed as the physical processor.
Each partition’s profile defines CPU entitlement that determines how much processing
power any given partition should receive. The total sum of CPU entitlement of all partitions
cannot exceed the number of available physical processors in a shared processor pool.
The number of virtual processors can be changed dynamically through a dynamic
LPAR operation.
The minimum number of virtual processors is equal to the entitled capacity rounded up to
the nearest whole number.
The maximum number of virtual processors is the smaller of the following items:
– Rounding up the number twenty times the entitled capacity
– The number of active cores in the system
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