[Gllug] What makes a USB device switch back to 1.1?

Christian Smith csmith at thewrongchristian.org.uk
Thu Jul 7 09:18:44 UTC 2011

On Tue, Jul 05, 2011 at 06:38:32PM +0100, John Winters wrote:
> I hit an interesting problem at the weekend.  A 2 TB Seagate USB drive  
> plugged into a nearly new Gigabyte motherboard would only work at 12  
> mb/s.  Looking at /var/log/syslog, whichever port it was plugged into a  
> message appeared saying it needed to be plugged into a high speed hub in  
> order to get anything better.
> The same drive plugged into a much older computer works fine at USB 2.0  
> speeds.
> What might be making the new one run slowly?  I tried both sockets on  
> the motherboard, and front-panel ones which are connected to header pins  
> on the m/b.  Could it be other USB devices on the same machine (keyboard  
> and mouse)?  Faulty wiring?
> I've checked the motherboard's BIOS setup screens.  According to the  
> documentation for the m/b there should be options to turn USB 2.0 on and  
> off, but they simply aren't there in the actual screens.
> Anyone any experience of what causes this sort of thing?

I'd check your dmesg output for any indication of problems between
the driver and the chipset.

Does this M/B have USB3? You might be able to tell from the socket
colour, which would be orange I believe. These use a different
HCI to USB2 (xhci vs ehci) so try "modprobe xhci-hcd".

At least telling us what the motherboard model is might help.

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