Microsoft KB Archive/943198

= When you use a USB-to-Serial converter to connect a device to a Windows XP-based computer, the data transfer from the computer to the device is slower than expected =

Article ID: 943198

Article Last Modified on 10/12/2007

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional

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SYMPTOMS
When you use a USB-to-Serial converter to connect a device to a Windows XP-based computer, the data transfer from the computer to the device is slower than expected.

For example, assume that you connect a Windows Mobile-based device to a Windows XP-based computer through an &quot;ActiveSync over serial&quot; port. In this situation, the data transfer from the computer to the Windows Mobile-based device is much slower than the data transfer from the Windows Mobile-based device to the computer.



CAUSE
This issue occurs because the Usbser.sys driver does not follow the USB specification. When the computer transfers data to a mobile device, the transfer process is based on the Usbser.sys driver. The Usbser.sys driver does not send zero-length packets when the total transfer size is an integer multiple of the packet size. However, zero-length packets are required by the USB specification so that the device can recognize when the packet transfer is finished.



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 on the computer.

Restart requirement
You must restart your 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 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, 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

Keywords: kbexpertisebeginner kbfix kbpubtypekc kbqfe kbhotfixserver KB943198

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