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

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.

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.

Service pack information

To resolve this problem, obtain the latest service pack for Windows Vista. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Hotfix information

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: 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:

1. Click Start
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   , type regedit in the Start Search box, and then click regedit.exe in the Programs list.
   
   
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   If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\msahci\Controller0
3. 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:
   1. On the Edit menu, point to New, and then click Binary Value.
   2. Type DipmEnabled for the name of the entry, and then press ENTER.
   3. Right-click DipmEnabled, click Modify, type 01 in the Value data box, and then click OK.
4. Exit Registry Editor.

A supported hotfix is 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 software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if 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. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

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, x86-based versions

Windows Vista, 64-bit versions

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Windows Vista Service Pack 1.

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