An energy efficient radio having a clocking system utilizing two clocks with very different precision and power characteristics. In another aspect, the time that a radio spends on listening/receiving is optimized so that energy is not wasted when there is no need to keep receiving. In another aspect, to further improve the energy efficiency, two receive portions with drastic difference in power consumption, instead of a single receive portion as is used in a typical wireless receiver, and are used to process different parts of a received packet.