Notebook computers, with Intel x86 processors, can run for a few hours on a battery charge while mobile phones, with ARM processor based chips, operate for a few days. Despite what ARM might like us to believe, this has little to do with the processor in each machine.
The difference between a few hours and a few days is a factor of about 24. The difference in area between the 3 inch display of a handset and the 15 inch display of a notebook computer is a similar factor of about 25. This is no coincidence.
The top 3 power consuming components of mobile device are:
1. The display
2. The radio (Wi-Fi, GSM, DVB-T, GPS) and/or disk drive
3. The speaker or headphone driver
With normal usage the processors in a mobile device typically consume less than 10% of battery energy. Even if one processor architecture used half the power of the other it could only improve battery life by about 5%.
Said another way, a notebook computer designed with an ARM processor would still have just a few hours battery life and a handset designed with an x86 (or a MIPS or even a free OpenRISC) based chip would still offer days of battery life. The advanced mobile processors from ARM and Intel are both DSP-extended, coherent multicore-capable, superscalar, and deeply pipelined. They are more similar than either company might like to admit.
Jonah Probell is CEO of YAP IP (http://www.YAPIP.com) and an impartial analyst of the microprocessor industry.