Você tem um único controlador USB3.0 - o "USB 3.0 eXtensible Host Controller".
De acordo com Intel (página 48 do documento):
The PCH contains one eXtensible Host Controller Interface (xHCI) controller and two Enhanced Host Controller Interface (EHCI) controllers. The xHCI controller is mapped as PCI D20:F0 and it supports up to 14 USB 2.0 ports of which 6 can be configured as SuperSpeed (USB 3.0) ports.
EHCI controller 1 (EHCI1) is located at D29:F0 and it supports up to 8 USB 2.0 ports.
EHCI controller 2 (EHCI2) is located at D26:F0 and it supports up to 6 USB 2.0 ports.