Microsoft KB Archive/932079

= Power consumption may be slightly more than expected on a portable Windows Vista-based computer that uses a SATA hard disk that does not support Host-Initiated Link Power Management =

Article ID: 932079

Article Last Modified on 8/29/2007

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APPLIES TO


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

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Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry



SYMPTOMS
Power consumption may be slightly more than expected on a portable Windows Vista-based computer. This problem occurs if the following conditions are true:
 * The computer is using a Serial Advanced Technology Attachment (SATA) hard disk that is using a SATA Advanced Host Controller Interface (AHCI) driver.
 * The hard disk supports Device-Initiated Link Power Management (DIPM) but does not support Host-Initiated Link Power Management (HIPM).
 * The computer is idle and running on battery power.

This problem may cause a slightly increased drain of battery power.

Note The increased power consumption is small and may not be noticeable to a typical user.



CAUSE
This problem may occur if the SATA hard disk does not support HIPM. In this case, Windows Vista may not use DIPM for power management. Therefore, the Windows Vista power management feature is less able to efficiently manage power consumption.

Note This problem may also occur if you modify a registry key to disable HIPM. This article does not address the scenario in which HIPM is disabled by using a registry key.



RESOLUTION
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To enable this hotfix, you must manually enable DIPM in the registry.

Note Do not apply this registry change if the hard disk does not support DIPM. Unexpected problems may occur if you apply this registry change and the hard disk does not support DIPM. Contact the manufacturer of the hard disk for more information about how to determine whether the hard disk supports DIPM. For information about how to contact the manufacturer of the hard disk, click the appropriate article number in the following list to view the article in the Microsoft Knowledge Base:

65416 Hardware and software vendor contact information, A-K

60781 Hardware and software vendor contact information, L-P

60782 Hardware and software vendor contact information, Q-Z

Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

To manually enable DIPM, add a registry entry named DipmEnabled, if one does not already exist. If the registry entry exists, you must give it a value of 1. To add or modify the DipmEnabled registry entry, follow these steps:  Click Start, type regedit in the Start Search box, and then click regedit.exe in the Programs list.

If you are prompted for an administrator password or for confirmation, type your password, or click Continue. Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\msahci\Controller0

 If the DipmEnabled entry already exists, right-click DipmEnabled, click Modify, type 1 in the Value data box, and then click OK.

If the DipmEnabled entry is not listed, follow these steps:  On the Edit menu, point to New, and then click DWORD Value. Type DipmEnabled for the name of the entry, and then press ENTER. Right-click DipmEnabled, click Modify, type 1 in the Value data box, and then click OK.</li></ol> </li> Exit Registry Editor.</li></ol>

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

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

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MORE INFORMATION
For more information about how hotfix packages are named, click the following article number to view the article in the Microsoft Knowledge Base:

816915 New file naming schema for Microsoft Windows software update packages

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

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

Additional query words: 64bit 64-bit

Keywords: kbbug kbfix kbqfe kbexpertiseinter kbhotfixserver KB932079

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