Method and apparatus for managing power in computer systems

A system comprising:

• a hierarchical configuration of a plurality of power domains and a plurality of power management members, each power domain supplying power to at least one power management member;
• a first power manager associated with a first power domain to determine when to change a power state of the first power domain within the hierarchical configuration;
• and
• a second power manager associated with a second power domain to determine when to change a power state of the second power domain within the hierarchical configuration based on the changed power state of the first power domain, wherein the second power domain supplies power to the first power domain, wherein the first and second power managers communicate with each other based on a hierarchical relationship that is similar to a hierarchical relationship between the first and second power domains.

A system comprising:

• a power management member;
• a child power manager adapted to select a power state for the power management member, said power state selected from at least three different power states;
• a parent power manager adapted to receive from the child power manager a notification of the selected power state;
• and
• a parent power domain to supply power to the power management member, wherein the parent power manager defines a power state of the parent power domain when an output power characteristic of the parent power domain is insufficient to satisfy the selected power state of the power management member.