This message was posted on behalf of Intel Corporation
The Intel® Desktop Board DP55KG has a PCIe 2.0 x16 slot, which theorically, can handle a PCIe 3.0 card (yours), the only thing that theorically will happen is the transfer speeds would work as PCIe 2.0 standard insteado of 3.0
It is good to mention that BIOS releases for this board were not tested with PCIe 3.0 technology since at that time it was not out yet, and the product is End of Interactive Support, for that reason, we cannot say that a PCIe 3.0 card would work with the Intel® Desktop Board DP55KG you own.
My recommendation would be getting a more recent board which has PCIe 3.0 support so you can take advantage of this technology and use the graphics card with the best scenario.
Hope this can clarify your inquiries and I hope you have a great week :)