I don't have all the specifics about the numbers, but I do have an external USB 3.0 device. I use and enclosure I can add whatever hard drive I want and I put in a SATA II drive. Don't know what the numbers are, but if you tell me how your are measuring and what type of file you are transferring, I will check mine.
I do have special ports that are colored red and made sure to load the drivers for the 3.0 controller.
Is you cable larger than a normal USB 2.0 cable?
If you plug the device into a 2.0 port, do you get a message about transferring faster if you use a 3.0 port?