1. A method for switching a computer system, including a first processor, a second processor, and a common memory connected to the second processor, from a low power mode, in which at least a portion of the first processor is active, to a high performance mode, in which at least a portion of the first processor and at least a portion of the second processor are active, the method comprising: powering on at least a portion of the second processor; quiescing traffic from the first processor to the common memory; and switching paths used by the first processor to access the common memory from a first path across the second processor to a second path across the second processor.