WINDOWS 1002000 PROFESSIONAL RESOURCE KIT [Electronic resources] نسخه متنی

Understanding the Advanced Configuration and Power Interface

For the OnNow system to work correctly, Windows 2000 Professional must be aware of how power management features integrate throughout the computer. This is done through the Advanced Configuration and Power Interface (ACPI), a system interface that provides a standard method for managing power consumption by the computer hardware. ACPI allows the motherboard to describe its device configuration and the interface of its power control hardware to Windows 2000 Professional. This allows the operating system to automatically turn on and turn off standard devices, such as disk drives, network adapters, and printers, as well as other electronic devices that might be connected to the computer, such as VCRs, TVs, telephones, or stereos.

ACPI allows the operating system to have direct control over how the computer consumes power. It can control when the computer enters and leaves sleep states. It also allows the operating system to put individual devices, including the CPU, into low-power states based on usage. The parameters that determine the behavior of the power management system can be configured using power schemes. Power schemes determine battery management policy and also allow you to define the point at which the system, the monitor, and the disk drive enter a sleep state in different circumstances. For more information about power schemes, see "Configuring Power Schemes" in this chapter.

ACPI Overview

To use all the features of OnNow, the system BIOS must support ACPI. The BIOS plays an important role in the ACPI by working with Windows 2000 Professional to perform the necessary initialization and hand off during system start up and when resuming to the working (full power) state.

Windows 2000 Professional Setup contains checks that prevent ACPI from working on a computer with a BIOS that does not support ACPI or does so incorrectly. Before you upgrade a computer to Windows 2000 Professional, you should determine whether it has a BIOS that supports ACPI. To do so, you can use the Microsoft System Information (MSInfo) utility to get the computer's type and BIOS version. To check to see if your BIOS is up-to-date, see the Hardware Update link on the Web Resources page at http://windows.microsoft.com/windows2000/reskit/webresources.

Once you upgrade to Windows 2000 Professional, you can check whether support for ACPI is installed on a computer by checking the list of system devices in Device Manager. You must use the Devices by connection view to do this. Under the Computer node, you should see Advanced Configuration and Power Interface (ACPI) PC (or in the case of a computer with multiple processors, the PC is replaced with MP).

Figure 20.2 shows the relationship of the various components that constitute a computer system that uses ACPI.

Figure 20.2 Relationship Between System and ACPI Components

NOTE

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Windows 2000 Professional provides very limited support for computers with a BIOS that does not support ACPI. With such systems, the power management features of Windows 2000 Professional function, but the BIOS must control power management.

The ACPI specification has two parts: configuration and power management. ACPI gives Windows 2000 Professional and the device drivers complete control of power management. The BIOS simply provides Windows 2000 Professional with access to the hardware controls for controlling power in the system. Windows 2000 Professional and the device drivers, which already know when the system is active, decide when to turn off devices that are not in use and when to put the entire system to sleep. For more information about the ACPI specification, see the ACPI link on the Web Resources page at http://windows.microsoft.com/windows2000/reskit/webresources.

Because power management is controlled by the operating system, there is a single user interface for managing power that works on all ACPI computers and simplifies the experience for the end user. ACPI provides more detailed information to the operating system about what the system can do and about the sources of events.

For example, a computer, operating system, and application that uses ACPI can do the following:

Make sure the screen does not turn off in the middle of a presentation.

Let the computer wake automatically in the middle of the night to perform some task, yet not turn on the monitor and drives needlessly.

Let the user choose what the power and sleep buttons do to the system.

During Windows 2000 Professional Setup, ACPI is installed only on systems that have an ACPI-compatible BIOS. If you need to update your BIOS to support ACPI, you can do so using the following procedure.

To enable ACPI

Update (flash) the BIOS to the latest version. (see the manufacturer's Web site for instructions about how to do this with your particular computer.)

Reinstall Windows 2000 Professional.

NOTE

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You do not need to reinstall Windows 2000 if you had an ACPI-compliant BIOS and then upgraded to a newer ACPI-compliant BIOS. You only need to reinstall Windows 2000 if you did not have an ACPI BIOS or an ACPI-compliant BIOS before you upgraded the BIOS.

Advanced Power Management Support

Advanced Power Management (APM) is the previous version power management solution that was introduced in
Windows 95. ACPI supercedes APM. While Microsoft strongly recommends using systems with an ACPI-capable BIOS,
Microsoft recognizes that many computers only support APM.

Windows 2000 Professional has limited support for APM, and that support is intended only for older portable computers. It is not designed for use on desktop computers or other computers that do not use batteries for system power.

Microsoft places portable computers in one of three categories based on the support for APM offered by the systems. Windows 2000 Professional recognizes the following categories:

AutoEnable APM During installation of the operating system, Windows 2000 Professional Setup automatically installs and enables APM on systems in this category, and the APM tab is present when you open Power Options in Control Panel.

Disable APM Microsoft has determined through testing that APM does not work properly on systems in this category. During installation of the operating system, Windows 2000 Professional Setup does not install APM. The APM tab is not present in Power Options.

Neutral Systems The APM functionality of systems in this category has not been determined. During installation of the operating system, Windows 2000 Professional Setup installs APM, but does not enable it. You can manually enable APM support on the APM tab of Power Options in Control Panel.

For more information about APM, see "Mobile Computing" in this book. For more information about APM and ACPI BIOS detection, see the Microsoft Knowledge Base link on the Web Resources page at http://windows.microsoft.com/windows2000/reskit/webresources. Search for the articles "Windows 2000 and Advanced Power Management (APM) Support" and "How Windows 2000 Determines ACPI Compatibility."