1. An apparatus comprising: an input/output (I/O) device adapted to implement a layered protocol stack for communication on a serial interconnect, the I/O device including, receiving logic adapted to receive a power state request referencing a power state; storage adapted to hold a referencing to the power state associated with a plurality of power sub-states; and configuration logic adapted to select a power sub-state of the plurality of power sub-states based at least in part on an algorithm relating power consumption associated with the I/O device to a performance metric associated with the I/O device and to configure the I/O device according to specifications of the power sub-state in response to selecting the power sub-state.