Power

Desktop computers usually attain its power from internal power supplies that plug into the wall. These power supplies are large, weigh a fair amount, and need a cooling fan to prevent over heating. The purpose of the power supply is to convert the AC input into lower DC voltages that the computer hardware can use. The current power supply standard is called ATX.

Handheld computers rely on a fixed energy source. Since handhelds are constantly mobile, batteries are the only feasible solution for powering the device. This puts enormous constraints on the hardware to perform at lower power consumption levels. This is one of the impeding issues that portable hardware manufactures are dealing with.

In addition, handheld computers need to be small and light. Decreasing overall power consumption in a device will decrease the overall weight since it requires fewer batteries to run. Handhelds must also emit less heat then a desktop computer since the device has to be handled. Cooling the processor in a handheld is not a good idea since fans consume more power and their isn't enough room in the device for one.

Power consumption is an issue that stretches over all aspects of handheld computer design including the processor, data storage, display, networking, and any peripherals. Handhelds tend to run on 2 AAA batteries and on most Palm models last 2 months under typical use. As the technology becomes more energy efficient we will see an increase in the developments of processor speed, networking, and visual displays until it can rival the muscle of the desktop.

For more information check out:

http://www.howstuffworks.com/power-supply.htm
http://guir.cs.berkeley.edu/projects/p6/finalpaper.html
http://www.palmpower.com/issues/issue199805/processor003.html