From: Mobile and disconnected computing

Current battery technology limits PDA use to only a few hours.  The
conservation of power through system software is thus becoming a major
area of research in mobile computing.  Two specific approaches to this
problem exist.

- Some researchers [Greenawalt, 93] are attempting to analyse the effects
  of application type, user input and operating system implementations on
  device power consumption.  Based upon simulation data, several power
  consumption models have been proposed for disks [Greenawalt, 93]
  [Douglis & Marsh, 93].  Work in characterising and analysing the power
  consumption problem is still ongoing.

- Several industry-led efforts, on the other hand, have focussed on
  building system support for dynamic power-saving mechanisms.  The
  Advanced Power Management standard presents an interface and structure
  for manipulating power consumption.  The Nomadic System Group at Sun
  Microsystems has integrated similar support into SVR4 [Bender et. al,
  93]; these facilities are also available in QNX.

Complete analysis of peripheral device power usage and experimentation
with different strategies for implementing power management will certainly
be useful.