there is not a pice 2.0 processor, is LGA1155 processorhttp://www.gigabyte.com/products/product-page.aspx?pid=4090#ov
said is supported
In answer to this, the original Sandy Bridge processors only support upto PCIe 2.0 interfaces. When the newer Ivy Bridge motherboards came along with the faster PCIe 3.0 interfaces they needed an Ivy Bridge processor to run them as PCIe 3.0. Although the Ivy-Bridge motherboards were backward compatible and would run with Sandy Bridge processors they were restricted to PCIe 2.0 speeds on the PCIe interfaces.
However, all this is purely academical as there is nothing in the build that actually requires PCIe 3.0.