On Monday 19 September 2005 01:47 pm, you wrote: > On Mon, 19 Sep 2005, Jason D. Sommerville wrote: > > On Monday 19 September 2005 09:09 am, you wrote: > > > > I've done a little more testing, and if I plug the drive into ports > > > > 0,1 or 4 (my own arbitrary numbering) it is recognized as a USB 1.0 > > > > device. Ports 2 and 3 it connects as a 1.1 device. > > > > > > (I assume you mean that in ports 0, 1, and 4 it runs at high speed, > > > whereas in ports 2 and 3 it runs at full speed. It will always be > > > recognized as a USB 2.0 device no matter what port you use; you check > > > this by looking at the "Ver=" field on the D: line in > > > /proc/bus/usb/devices.) > > > > No, I mean full speed as opposed to low speed. It never connects as a > > high speed device. (Otherwise I'd just use the working plug and not > > bother you guys!) > > Oh, okay. If your drive _ever_ connects at low speed then there's > something very wrong either with it or with the PCI card. Can you post > the /proc/bus/usb/devices entry, and maybe also the dmesg log, for this > situation? The logs you posted before show full-speed connections. > > > I get the impression that the hub to which the connects (the 2.0 hub, vs. > > the 1.1 hub, etc.) is a decision entirely made by the hardware. Is that > > correct? > > No, not really. You also have to understand that the card contains only > two types of controller: high speed (EHCI) and full/low speed (OHCI). > There is no separate low-speed controller; low-speed connections are > handled by the OHCI controller. > > When the device first connects, it talks to the EHCI controller. If it's > a low-speed device, the controller realizes it from the initial electrical > signal levels and doesn't do anything more. Otherwise the driver tells > the EHCI controller to reset the device, and if the device is capable of > operating at high speed then during the reset it exchanges various > electrical signals with the controller to let it know. When the reset is > done, the connection is running either at full speed or high speed. But > the EHCI controller can't handle full-speed communications. So for low- > or full-speed devices, the driver software tells the hardware to switch > the connection over to the companion OHCI controller. > > Broadly speaking, the hardware determines the capabilities but the > software determines which controller is actually used. > > Alan Stern
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