Sabertooth with an FX-8320 PCI Lanes

Solution
For AMD FX series cpu, the answer is not due to the processor. There is no IGP embedded into the FX processor, so the Northbridge chip primarily functions as a controller for the fx processor. But intel cpu, like 5930k, it has the its own on-die PCI Express controller.
For the 990FX MB, the pice config =2x16 or 4x8. More info http://en.wikipedia.org/wiki/AMD_900_chipset_series