HDD transfer rate decrease with USB devices connected

[wing0]

I've been searching up the culprit to this problem for a while.

Currently, I have a Athlon XP 2000+ system(I know it's old...but meh...no job)
with KT266A chipset motherboard that has USB2.0

HDD: Maxtor DiamondMax 9 80GB ATA133

The hdd itself is running fine, getting around 45MB/s transfer rate and is set to UDMA6 mode(133). Tested with hdtune

Problem occurs when I have an usb external hdd or usb memory drive connected to the system. My transfer rate will drop to around 16-17MB/s, once I unplug the usb device, it goes back to normal.

I'm using the usb2.0 driver from XP SP2 right now and just don't know what's going on. I have also tried two version of VIA 4-in-1 drivers, one is legacy but optimized for older generation NB, and the newest one. Both exhibits the same problem.

Searching online doesn't really reveal anything...and also this dosen't happen to my other computer which is a P4+865PE with the same hdd.

Can somebody please let me know what I'm missing here.

 

[TeeJay1952]

Use a powered USB hub or external drive, (just guessing from your info)

 

[wing0]

This problem only occur when I have an external drive attached to the system. If I have a usb mouse attached, there would be no slowdown to transfer rate. Only when I have external hdd or usb memory stick, then the hdd transfer rate would go down to the same transfer speed of the usb device(very weird).