How many USB buses do Mac Pros have?
My new Mac Pro has 6 "USB" busses, 12Mb/s, and two "USB High Speed" busses. 480 Mb/s.  One of the "USB" busses shows Bluetooth on it, but none of the others seem to be in use.  The external connectors belong to the two "High Speed" busses.  Buss 0xfd has one of the front and two of the back connectors.  Buss 0xfa has one of the front and one of the back connectors.