Power Management

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 computers 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



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

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

  2. Reinstall Windows 2000 Professional.



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.