Low perfomance when read from usb flash drive

[Artyom Mirgorodsky]

>I know that certain AMD USB controllers perform less with the new USB stack, 
>but I've not been able to track down the issue.

Yes, I have AMD platform (motherboard ASUS A8N-VM-CSM)

>Can you try another PC having another CPU brand?

Yes, I have already posted the result - 22 Mb/sec, much better than on my computer.

>There might be some minor things that needs tuning like the NAK retry counter. 
>I suspect you have run into a timing issue with the hardware.

Can I do anything to solve this problem or at least help you to track it down?