Describe How to Configure Power Settings

One of the most popular features of a laptop is the ability to operate using batteries. This feature allows laptops to operate in locations where AC power is not available or is inconvenient. Advances in power management and battery technology are increasing the time laptop users can remain disconnected from AC power. Current batteries can last from 2 to 10 hours without recharging. Managing the power by configuring the power settings on a laptop is important to ensure that the battery charge is used efficiently.

The Advanced Configuration and Power Interface (ACPI) standards create a bridge between the hardware and OS and allow technicians to create power management schemes to get the best performance from the computer. The ACPI standards can be applicable to most computers, but they are particularly important when managing power in laptops. Table 6-5 shows information about each power state.

Table 6-5 Power Management States

ACPI Standard

Power Management State


The computer is on and the CPU is running.


The CPU is not running. However, the CPU and RAM are still receiving



The CPU is off, but the RAM is refreshed. The system is in a lower

power mode than S1.


The CPU is off, and the RAM is set to slow refresh rate. This mode is

often called "Save to RAM." In Windows XP, this state is known as the

Standby mode.

ACPI Standard

Power Management State


The CPU and RAM are off. The contents of RAM have been saved to a

temporary file on the hard disk. This mode is also called "Saved to

Disk." In Windows XP, this state is known as the Hibernate mode.


The computer is off and nothing has been saved.

Technicians frequently are required to configure power settings by changing the settings found in BIOS. Configuring power settings in BIOS affects the following conditions:

u System states u Battery and AC modes u Thermal management u CPU PCI bus power management

Figure 6-14 shows an example of power settings in BIOS.

Figure 6-14 BIOS Settings

Figure 6-14 shows an example of power settings in BIOS.

Select Screen


Select Itea

Change Option


General Kelp


Save and Exit


When working in Windows XP, the ACPI power management mode must be enabled in BIOS to allow the OS to configure all the power management states. There is no standard name for each power management state. Manufacturers can use different names for the same state.

Here are the steps to check the ACPI settings in the BIOS:

Enter BIOS setup by pressing the appropriate key or key combination while the computer is booting. Typically this is the Delete key or the F2 key, but there are several other options.

Locate and enter the Power Management Settings menu item. Use the appropriate keys to enable ACPI mode. Save and exit BIOS setup. Note

These steps are common to most laptops and should be used only as a guideline. Be sure to check your laptop manual for specific configuration settings.

The power options in Windows XP allow you to reduce the power consumption of a number of devices or of the entire system. Power options allow you to control the power management features of the following:

■ Shut Down, Hibernate, and Standby modes

■ Low-battery warnings

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