When "USB 2.0 controller" is disabled in BIOS, I noticed some USB ports are not available.
This is chipset limitation. ICH9 embedded two EHCI Host Controllers and six UHCI Host Controllers, supporting up to twelve USB ports.
When USB 2.0 controller is (set) disabled , EHCI #2(EHCI Host Controllers)and UHCI#4 ,UHCI#5 ,UHCI#6(UHCI Host Controllers) are not available.
Therefore, rear USB ports are not available and only front USB ports are available.