Hi!
This is an interesting post. Unfortunately not answered.
I have comparable problems with Intel USB3.0 eXtensible Host Controller myself.
I have a dell optiplex 3020 with Intel 8 series chipset and Win7 proffesional. High speed devices do perform well, but the Full speed devices are slow. While the same FS device processes a number of commands on an Intel chipset 6 in 4-5 ms, the Intel chipset 8 needs 20ms or more. This has been verified with USBlyzer.
It seems that my 2.0 devices all are managed by the xHCI controller instead of the conventional EHCI controller.
I want to configure 2.0 ports as 2.0 and 3.0 ports as 3.0 (mixed port mode) to check whether my FS devices operate well again.
Any help is appreciated and thanks in advance!
Martin