Microsoft KB Archive/938725

= Battery power may drain more quickly than you expect on a Windows Vista-based portable computer that has a USB SideShow-compatible device attached =

Article ID: 938725

Article Last Modified on 8/29/2007

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APPLIES TO


 * Windows Vista Home Premium 64-bit Edition
 * Windows Vista Business 64-bit Edition
 * Windows Vista Enterprise 64-bit Edition
 * Windows Vista Ultimate 64-bit Edition
 * Windows Vista Home Premium
 * Windows Vista Business
 * Windows Vista Enterprise
 * Windows Vista Ultimate

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SYMPTOMS
Power management may not work correctly on a Windows Vista-based portable computer that has a Windows SideShow-compatible USB device attached. Because of this problem, the CPU may not correctly enter a reduced power-consumption state. In a reduced power-consumption state, the processor is supposed to conserve battery power. The processor does this by using reduced voltage or reduced frequency states. When this problem occurs, the battery may drain more quickly than you expect.



RESOLUTION
Note After you install this hotfix, you must manually enable the USB selective suspend setting option. To do this, follow these steps:
 * 1) Click Start vistastartbutton.jpg], type power options in the Start Search box, and then click Power Options in the Programs list.

If you are prompted for an administrator password or for a confirmation, type the password, or click Allow.
 * 1) Under the selected power plan, click Change plan settings.
 * 2) Click Change advanced power settings.
 * 3) In the Power Options dialog box, expand USB settings, and then expand USB selective suspend setting.
 * 4) If you want to enable Windows Vista to turn off the USB root hub when the computer is running on battery power, click Enabled in the On battery list.
 * 5) If you want to enable Windows Vista to turn off the USB root hub when the computer is plugged into a power outlet, click Enabled in the Plugged in list, and then click OK.

Hotfix information
A supported hotfix is now available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. To create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Prerequisites
You must have the USB cumulative rollup for Windows Vista installed before you install this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

936003 USB cumulative rollup for Windows Vista

Restart requirement
You must restart the computer after you apply this hotfix.

Hotfix replacement information
This hotfix does not replace a previously released hotfix.

File information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Vista, 64-bit versions


STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
For more information, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates

Keywords: kbbug kbfix kbqfe kbprb kbexpertiseinter kbhotfixserver kbwinvistapostrtmfix KB938725

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