Apple Inc.
METHODS AND APPARATUS FOR SYNCHRONIZATION OF TIME BETWEEN INDEPENDENTLY OPERABLE PROCESSORS

Abstract:

Methods and apparatus for synchronization of time between independently operable processors. Time synchronization between independently operable processors is complicated by a variety of factors. For example, neither independently operable processor controls the other processor's task scheduling, power, or clocking. In one exemplary embodiment, a processor can initiates a time synchronization process by disabling power state machines and transacting timestamps for a commonly observed event. In one such embodiment, timestamps may be transferred via inter-processor communication (IPC) mechanisms (e.g., transfer descriptors (TDs), and completion descriptors (CDs)). Both processors may thereafter coordinate in time synchronization efforts (e.g., speeding up or slowing down their respective clocks, etc.).