Handheld devices have added more and more functionality over the past couple of years. Advances in wireless networks have contributed to this trend. However, the major factor has been the development of more powerful mobile processors. New mobile chips have given smart cellular phones, PDAs, and intelligent pagers the capability to run faster, access the Internet, handle multimedia, and offer other enhanced services. However, more powerful chips use energy more quickly - a problem in devices that run on batteries, which have limited life spans. In addition, the chips generate heat buildup in devices that don't have space for fans or other cooling mechanisms. In response, mobile-chip makers are developing low-power designs and working on other ways to lower energy consumption. However, they face important challenges in the process.