32-bit Cardbus usb 2.0 controller not performing anywhere near 480Mbps Windows XP
I have a 32-bit cardbus for usb 2.0 containing a NEC 720101 chipset and the description says it supports hi-speed 480Mbps yet even with a usb 3.0 device it only reaches near 18Mbps. I have tried changing the driver from what was obtained automatically by the windows update to something written for 98se/me but that didn't improve anything either.. I've tried installing different drivers to see if that would allow it to perform at its hi-speed but with no difference in speed.
Is there something different I may need to look at other than the driver?
It is self-powered (the 2 usb 2.0 ports with 3 other low-powered ports by the laptop itself) and the usb in question can at least reach 100Mbps on my other laptop so I know it's not the usb.
Any other information that I can give to help solve this please let me know. Even if you only have ideas rather than direct solutions I am willing to look at almost anything at this point.
OS: XP SP3
usb is powered using 150mA according to USB Root Hub Properties 'Power' tab but the 2 hi speed slots each hold 500mA and are the ones self-powered.