Abstract: In one embodiment, a processor includes a core and a power controller coupled to the core that in turn includes a self-test control circuit. The self-test circuit is adapted to: isolate the core during field operation; cause the core to execute at least one diagnostic test at a first operating voltage to identify a guard band voltage for the core; and cause the core to enter into a low power state after the execution of the at least one diagnostic test. Other embodiments are described and claimed.