Advanced Configuration and Power Interface Specification

Processor Configuration and Control
belong to a container if they are associated in some way, such as a shared cache or a low power
mode which affects them all.
Parent for cluster 0 and
cluster 1
System
Root
Cluster
0
Cluster
1
Higher Level
Lower Level
Cluster 0's children
Core0 Core1 Core2 Core3
Leaves
Figure 8-45 Processor Hierarchy
Figure 8-45 depicts an example system, which comprises a system level processor container, which
in turn contains two cluster processor containers, each of which contains two processors. The overall
collection is called the processor hierarchy and standard tree terminology is used to refer to different
parts of it. For example, an individual processor or container is called a node, the nodes which reside
within a processor container are called children of that parent, etc. This example is symmetric but
that is not a requirement. For example, a system may contain a different number of processors in
different containers or an asymmetric hierarchy where one side of the topology tree is deeper than
another. Also note that while this example includes a single top level processor container
encompassing all processors, this is not a requirement. It is legal for a system to be described using a
collection of trees.
The processor hierarchy can be used to describe a number of different characteristics of system
topology. The main example is shared power states, see the Low Power Idle states in Section 8.4.4
for details.
8.4.3.1 Processor Container Device
This optional device is a container object that acts much like a bus node in a namespace. It may
contain child objects that are either processor devices or other processor containers. This allows
representing hierarchical processor topologies. Each processor container or processor in the
Version 6.0 435