Power management

For users of portable battery-powered devices such as smartphones, tablets, and laptop computers, the ability to operate for long time periods without recharging is an important feature. Designers of portable systems place great emphasis on ensuring battery power consumption is minimized under all operating conditions. Some techniques designers use to reduce power consumption are as follows:

• Placing idle subsystems in a low-power state, or turning them off completely when they are not needed. This solution may not be possible for peripherals that must be available to respond to incoming requests, such as network interfaces.
• Reducing integrated circuit supply voltages and clock speeds during periods when execution speed is not critical.
• When possible, saving system state information and turning the processor power off completely. Users of laptop computers are familiar with two options for reducing power consumption when the system is not in use: standby...