Battery power may drain more quickly than you expect on a Windows XP SP2-based portable computer (918005)
The information in this article applies to:
- Microsoft Windows XP Professional
- Microsoft Windows XP Home Edition
SYMPTOMS
When you unplug the AC power from a Microsoft Windows XP-based portable computer, the battery may drain more quickly than you expect. Therefore, the operating system may shut down prematurely.
CAUSE This problem may occur if one of the following conditions is true:
- The portable computer cannot enter the deeper Advanced Configuration and Power Interface (ACPI) processor idle sleep states.
This occurs when the USB 2.0 driver leaves the asynchronous scheduler component running continuously. This prevents the processor from entering the deeper ACPI processor idle sleep states, or C-states. C-states save power when the processor is not busy. These states range from C0 to C3 or C4. Typically, an idle portable computer uses the C3 and C4 states to preserve battery power. If an idle portable computer cannot enter or maintain the C3 or C4 states, the battery power drains more quickly. This problem is fixed by installing the download that is available in this article. - The USB host controller is unable to turn off.
This typically occurs when devices are removed from a nested USB hub that is attached to the host controller. The host controller does not recognize the device removal. Therefore, the controller is never turned off. This prevents the processor from entering the ACPI processor idle sleep states.
This problem is not fixed by installing the download that is available in this article. - The USB host controller uses the periodic scheduler for USB 2.0 devices.
This typically occurs when devices that rely on the periodic scheduler are attached to the host controller. These may be isochronous (Isoch) devices such as audio devices. Alternatively, they may be interrupt devices such as mouse or keyboard.
This problem is not fixed by installing the download that is available in this article.
Note Various factors can affect the battery life of different portable computers that use different types of batteries. Therefore, you may not notice any improvement in battery life after you apply this update.
RESOLUTIONUpdate information
The following file is available for download from the Microsoft Download Center:  Download the Update for Windows XP (KB918005) package now.
For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to obtain Microsoft support files from online services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.
File information
The English version of this update 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. |
| Usbehci.sys | 5.1.2600.2891 | 30,080 | 19-Apr-2006 | 11:50 | x86 | SP2 | | Usbohci.sys | 5.1.2600.2891 | 17,152 | 19-Apr-2006 | 11:50 | x86 | SP2 | | Usbport.sys | 5.1.2600.2891 | 143,360 | 19-Apr-2006 | 11:50 | x86 | SP2 | | Usbuhci.sys | 5.1.2600.2891 | 20,608 | 19-Apr-2006 | 11:50 | x86 | SP2 |
STATUSMicrosoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
| Modification Type: | Minor | Last Reviewed: | 5/17/2006 |
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| Keywords: | kbQFE kbExpertiseBeginner kbHotfixServer KB918005 kbAudEndUser |
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