Requests are not transferred over the USB bus in the order in which they are submitted to the Windows USB driver stack on a multiprocessor computer that is running Windows Vista or Windows Server 2008

On a multiprocessor computer that is running Windows Vista or Windows Server 2008, when you try to transfer requests to a specific endpoint on a USB device, the requests are not transferred over the USB bus in the order in which they are submitted to the Windows USB driver stack.

This issue usually occurs when some requests contain zero-byte packets.

This issue occurs because of an error in the Microsoft USB Host Controller core driver (Usbport.sys). On a multiprocessor computer, after the requests are submitted to the Windows USB driver stack, some pending requests in the stack may not be added to the host controller's transfer queues in order of submission.

Hotfix information

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.

Important Windows Vista and Windows Server 2008 hotfixes are included in the same packages. However, only one of these products may be listed on the �Hotfix Request� page. To request the hotfix package that applies to both Windows Vista and Windows Server 2008, just select the product that is listed on the page.

Prerequisites

To apply this hotfix, you must have Windows Vista Service Pack 1 or Windows Server 2008 installed on the computer.

Restart requirement

You have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix replaces the following hotfixes:

• Hotfix 946723
• Hotfix 948643
• Hotifx 947382
• Hotfix 948229
• Hotfix 908673
• Hotfix 951720
• Hotifx 951720
• Hotfix 949201
• Hotfix 956388
• Hotfix 955840

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 Vista and Windows Server 2008 file information note

The MANIFEST (.manifest) files and the MUM (.mum) files that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008 and for Windows Vista" section. MUM files and MANIFEST files, together with the associated security catalog (.cat) files, are critical to maintaining the state of the updated component. The security catalog files, whose attributes are not listed, are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows Server 2008 and Windows Vista

For all supported x64-based versions of Windows Server 2008 and Windows Vista

For all supported Itanium-based versions of Windows Server 2008

Some USB client driver developers may work around this issue by limiting the number of pending USB transfer requests to a very small number (less than 4) for each USB endpoint. Also, USB client driver developers may work around this issue by delayingnew requests until previous requests for a specific USB endpoint have been completed.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Usually, USB transfers that are submitted to a single USB endpoint on a USB device will be transferred and completed in the same order in which they were submitted. This hotfix guarantees the ordering between USB transfers submitted for different endpoints.

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

Additional file information for Windows Server 2008 and Windows Vista

Additional files for all supported x86-based versions of Windows Server 2008 and Windows Vista

Additional files for all supported x64-based versions of Windows Server 2008 and Windows Vista

Additional files for all supported Itanium-based versions of Windows Server 2008