Microsoft KB Archive/941837

= A Windows XP Service Pack 2–based computer that has an Intel processor may experience high power consumption when the processor is idle and when there is a discontinuity in the C-states that are reported by the BIOS =

Article ID: 941837

Article Last Modified on 10/8/2007

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional

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SYMPTOMS
A Windows XP Service Pack 2–based computer that has an Intel processor may experience high power consumption when the processor is idle. This issue occurs when there is a discontinuity in the C-states that are reported by the computer's BIOS.

For example, consider the following scenario:
 * On a Windows XP Service Pack 2–based computer that has an Intel processor, the BIOS reports only the C1 C-state and the C3 C-state. The BIOS does not report the C2 C-state.
 * You let the computer and the processor become idle.

In this scenario, the processor driver does not use the C3 C-state. Instead, the processor remains in the C1 C-state. Therefore, the computer does not exploit the low-power capabilities of the C3 C-state. This issue specifically affects processor power consumption when the processor is idle.



CAUSE
On a Windows XP Service Pack 2-based computer, the Intel processor driver (Intelppm.sys) does not handle discontinuous C-states correctly.



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 Windows XP 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 Windows XP Service Pack 2 installed.

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

Hotfix replacement information
This hotfix does not replace any other previously released hotfixes.

Registry information
To use this hotfix, you do not have to make any changes to the registry.

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 XP with SP2, x86-based 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 about Intel Nehalem processor, visit the following Intel Web site:

http://www.intel.com/technology/architecture-silicon/next-gen/index.htm?iid=technology_next-gen+body_overview

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.

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

940566 An update is available to support Deep Power Down technology on a Windows XP S-based computer that has an Intel Penryn processor

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

941838 A Windows Server 2003–based computer that has an Intel processor may experience high power consumption when the processor is idle and when there is a discontinuity in the C-states that are reported by the BIOS

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: intelppm.sys

Keywords: kbfix kbexpertiseadvanced kbpubtypekc kbqfe kbhotfixserver KB941837

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