AUSUS 52x USB2 bit perfect?

I have been trying to find a 52x USB2 drive that is bit perfect. CloneCD say that all of the ASUS IDE drives are bit perfect or at least the 52x and a bunch of others but they do not have info on the USB one. I have already tried the Iomaga 52xUSB2 and it was a waste of tme (and money). My Liteon 40x USB2 is bit perfect so I know it is not the USB standard but the drive. I also got an ide Liteon in a USB2 box and that was not what I wanted

The ASUS uses a kind of buffer underrun technology that I am not familiar with and I really need help with this. The reason for all of this is too long to go into but can someone help with it? Could the ASUS 52x USB2 be bit perfect like the IDE one? And if no one knows can someone lead me to a way to find out. :bow: :bow: