[coreboot] [GSoC] option rom problems with DBM690T+VT6202L

Peter Stuge peter at stuge.se
Wed Jul 29 03:58:53 CEST 2009

Jason Wang wrote:
> The card has two UHCI controller and one EHCI controller.

Note that it is not in fact a UHCI controller if it supports USB 2.0.
It is difficult (maybe impossible) to find a UHCI PCI card.

An EHCI controller will only and always communicate with high-speed
devices using EHCI.

The EHCI controller and it's so-called companion controllers do not
mirror each port. Any connected device will only appear attached to
one controller, and it will always be the same controller for a given
device and a given physical port.

In other words, for you to be able to use UHCI with this PCI card,
you must attach a USB 1.1-only MSC device to one of the ports.

Please have a look at the EHCI standard[1] for more details, and feel
free to ask questions. Especially Figure 1-1 and the descriptions on
the same page (3) are very good for getting a better understanding of
these parts of USB.


[1] http://www.intel.com/technology/usb/download/ehci-r10.pdf

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