Who Killed My Battery?

Power consumption in mobile devices

Jonah Probell

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 Probell is CEO of YAP IP and an impartial analyst of the microprocessor industry.

© Copyright 2009 Jonah Probell