Not the OP, but USB3 can interfere with wireless communications (wireless mice seem highly susceptible). I've had some devices/cables/connections where usb3 was unreliable, and it would be better to use usb2 at much slower speeds.

I was trying openbsd and the xhci driver was dropping the external usb drive I had the system on crashing it, The vague hope was that forcing ohci would make the it stable enough to use.