If you’re using Microsoft Windows XP SP2 (Service Pack 2) and try to use 1394a or 1394b FireWire devices such as external hard drive, the performance of the FireWire devices are greatly decrease and not optimum. The slowness of FireWire devices especially obvious when you transfer, copy or backup your files and documents in your computer local drives to the FireWire connected external portal disk, or when you transfer and copy your photos from digital camera that uses FireWire connection.
Normally Firewire 400 and Firewire 800 devices and drives will operate in the range of 26 to 39 megabytes per second on file copy operations in which termed as S800 and S400 speed. However, if you install Windows XP SP2 or are using Windows XP SP2, the FireWire 1394b ports will be changed to S100 speed, instead of using S400 or S800 speed. So if you connect any 1394a or 1394b FireWire 400 or 800 device or external hard disk to a 1394b port, the FireWire devices incorrectly run at S100 or about 100 megabits per second, which is the cause for the slow FireWire transfer rate.
The resolution to the issue is to install an update for Microsoft Windows XP SP2 KB885222. It’s a hotfix released by Microsoft and described in Knowledge Base article KB885222 that corrects this issue. After installing the patch, restart the computer for it to take effect.
If you add a host controller for a new 1394 device to your computer after installing the KB885222 hotfix, you must add or modify the SidSpeed entry in the Windows registry for the new 1394 host controller to 1 of the following value:
0 for S100 speed
1 for S200 speed
2 for S400 speed (default value)
3 for S400/S800 speed (Windows XP Service Pack 1 [SP1] value)
The steps and instructions to add or modify the SidSpeed registry value are listed on the above mentioned Knowledge Base article, with additional information to locate the FireWire controller information necessary to modify the registry value.