A multi-core processor provides a configurable resource shared by two or more cores, wherein configurations of the resource affect the power, speed, or efficiency with which the cores sharing the resource are able to operate. Internal core power state management logic configures each core to participate in a de-centralized inter-core power state discovery process to discover a composite target power state for the shared resource that is a most restrictive or power-conserving state that will not interfere with any of the corresponding target power states of each core sharing the resource. The internal core power state management logic determines whether the core is a master core authorized to configure the resource, and if so, configures that resource in the discovered composite power state. The de-centralized power state discovery process is carried out between the cores on sideband, non-system bus wires, without the assistance of centralized non-core logic.