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Power Management on a Windows XP Professional Laptop

If you're primarily a laptop user, you'll find that the power management that originated in Windows2000 is included in Windows XP Professional, along with 30–40% more features to customize just how you want your laptop to use power, and when. The series of pages in the Power Options dialog box is easy to navigate as always. There's also the addition of a page in the Power Options Properties dialog box that includes a sliding scale that defines when both low and critical battery alarms will go off. This is a welcome change from the power management features in Windows 98 today, in which the levels for low and critical battery alarms are not configurable and—depending on the level of support from the manufacturer—can shut off a laptop without warning. The Alarm Action button also opens up a series of selections for choosing a power-down sequence for your applications. This is particularly useful for those users of laptops that run login sessions with mainframes through Rumba, for example, in which an abrupt log-off can take multiple retries to connect to. Clearly, the Alarm Action button was created from the complaints of users who are running terminal emulation software that can take multiple retries to get reconnected. Figure 2 shows the Alarms page of the Power Options Properties dialog box.

Figure 2 Using the sliding scales on the Power Options Properties dialog box, you can configure when the low battery and critical battery messages are invoked.

There's also the series of Power Schemes that were defined in previous versions of Windows NT and Windows 2000. Microsoft has chosen to include the option of turning off the monitor and hard disks when both the system is plugged into an AC outlet and when it is running on batteries, as well. There are also the options for defining the System Standby and System Hibernate variables in the Power Schemes areas of the dialog box. Figure 3 shows the Power Schemes page of the Windows XP Power Options Properties dialog box.

Figure 3 Power Schemes are still present in addition to the options for having the monitor and hard disks turned off, whether running on battery or AC power.

The Hibernate mode now has its own page as well in this dialog box. For the first time, Microsoft is actually explaining what happens when a system goes into Hibernate mode. Data included in the system's RAM are written to disk when the system invokes Hibernate mode. There's the requirement of having sufficient disk space to handle the writing of data, and this dialog box in the Power Options Properties dialog box provides a calculation of what's needed to handle the task of writing to disk. Figure 4 shows the Hibernate page of the Power Options Properties dialog box.

Figure 4 The Hibernate page of the Power Options Properties dialog box calculates the necessary disk space for saving work in RAM when the system shuts down.

After leaving the IBM ThinkPad running for nearly two-and-a-half hours, the first power warnings kicked in, followed by the critical warning. The laptop had been configured for Hibernate mode. The system dutifully shut itself down. Reapplying power, I found the restore from Hibernate to be slow yet deliberate; the hard disk was being accessed constantly, and the data eventually arrived back after about three to four minutes. Not bad for the first release of an operating system, yet the space taken for the Hibernate file was actually 12% more than was stated in the dialog box; 140MB was taken when the dialog box claimed it would take 125MB. This was a minor issue, yet it shows that the interpolation of disk space for Hibernate mode is inaccurate in this first release of Whistler. The only time the IBM ThinkPad actually went into a deep Hibernation was after letting the system run out of power with the screen down. Apparently, Whistler thought the system was to go into deep Hibernation with the screen down, which requires a cold boot to get the ThinkPad back up and running.

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