-
Asus P9X79 Pro and WS PCIe layouts
These diagrams are remixed from the Asus website and the respective product owners manuals.
Asus P9X79 WS

Asus P9X79 Pro

While the WS may look like it has more PCIe bandwidth than the Pro, each board has a maximum of 40 lanes, which is limited by the PCIe capacity of the CPUs that these boards are designed for.
Just because a slot is x16 in size doesn’t mean it can provide X16 lanes in any or in all configurations.
Hope this is useful.
John