1. A computing device for managing power during a processor core activation cycle, the computing device comprising: a processor control module to (i) determine a number of active processor cores of a processor of the computing device and (ii) receive an activation request for at least one hibernating processor core of the processor of the computing device, wherein the activation request includes a command that the at least one hibernating core become active; and a power management module to (i) determine a new operating limit for each active processor core based on the number of active processor cores and the activation request, (ii) set an operating limit of each active processor core to the new operating limit, and (iii) cause, in response to the activation request, activation of the at least one hibernating processor core subsequent to setting the operating limit of each active processor core.