Power Management

Power Management The power-management system in Windows 2000, Windows XP, and Windows Server 2003 is an integrated approach to power management within the whole computer system (for both hardware and software)
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Power Management Power ManagementThe power-management system in Windows 2000, Windows XP, and Windows Server2003 is an integrated approach to power management within the whole computer system(for both hardware and software). This means that the computer system supporting powermanagement must include both hardware and software support for the followingfunctions: Minimum time expenses for startup and shutdown. This means that the system may stay in a hibernation state as long as necessary. It may wake up from this mode very quickly (this doesnt require rebooting). Efficient and economic power consumption, meaning an increase in the working life of the hardware. Devices consume power only when they process a system request or perform operations requested by the user. Devices that arent in use during a specified time period are switched to a sleeping state, and subsequently wake-up as needed. Silent operation.Requirements for power-aware hardware and software are defined by the OnNowinitiative. Windows XP and Windows Server 2003 provide this support and both the PCas a whole and each individual device consume the minimum amount of power (if thehardware meets the OnNow requirements). Notice that power management and PnP areinterrelated and depend on each other.This approach provides the following advantages: Intelligent behavior by the system. The operating system and applications work together to operate the PC, delivering effective power management in accordance with your current needs. For example, applications wont inadvertently keep the PC busy when they arent necessary, they proactively participate in shutting down the PC to conserve energy and reduce noise. Improved robustness and reliability. Higher level of integration.By using the Power Options applet in the Control Panel, it is possible to decrease energyconsumption by any device installed in the system. However, this is only the case if youhave an ACPI-compliant computer system.The Power Schemes TabTo start the Power Options applet, proceed as follows:1. From the Start menu, select Settings | Control Panel. Double-click Power Management.2. The Power Options Properties window will appear (Fig. 5.13). Figure 5.13: The Power Schemes tab of the Power Options Properties window3. To reduce the power consumption of your computer devices - or of your entire system - choose a power scheme, which is a collection of settings that manage the power usage of your computer. You can select one of the existing power schemes or create a user-defined power scheme. For example, depending on your hardware, you can do the following: Specify the conditions where the system will automatically turn off your monitor and hard disks to save power. Put the computer on standby if it is idle for a long period of time. While on standby, your entire computer switches to a low power state, where devices such as the monitor and hard disks turn off and your computer uses less power. When you want to use the computer again, it comes out of standby quickly, and your desktop is restored exactly as you left it. Standby is particularly useful for conserving battery power in portable computers. Put your computer in hibernation. The hibernate feature saves everything in memory on disk, turns off your monitor and hard disk, and then turns off your computer. When you restart your computer, your desktop is restored exactly as you left it. It takes longer to bring your computer out of hibernation than out of standby.Table 5.2 lists the registry keys that you can modify using the Power Schemes tab of thePower Management Properties windows. Table 5.2: Registry Keys Modified Using the Power Schemes Tab ControlsPower Schemes option Registry keyPower schemes HKCU\Control Panel\PowerCfg\CurrentPowerPolicyStandby detection threshold values (for the Binary-encoded parameterssystem, monitor, hard disk-System HKCU\Control Panel\hibernates, Turn off monitor, Turn off PowerCfg\PowerPolicies\n\Policieshard disks fields, respectively)Deleting the power scheme (the Delete Deletes the following keybutton) HKCU\Control Panel\PowerCfg\ PowerPolicies\n\Policies Decreases the following index counter: HKLM\SOFTWARE\Microsoft\Windows\ CurrentVersion\Controls Folder\PowerCfg\LastIDAdding new power scheme (the Save As Adds new subkey under the following key:button) HKCU\Control Panel\PowerCfg\ PowerPolicies\n\Policies Increases the following index counter: HKLM\SOFTWARE\Microsoft\Windows \CurrentVersion\Controls Folder\PowerCfg\LastIDGenerally, you need to turn off your monitor or hard disk for a short period of time toconserve power. The most convenient mode for this is the standby mode, which puts yourentire system in a low-energy state.The Hibernate TabBeside the standby mode, the Power Options applet allows you to put your system intohibernation mode. As already mentioned, the hibernate feature saves everything inmemory on disk, turns off your monitor and hard disk, and then turns off your computer.After rebooting the system, your des ...