Does the Intel S1200BT motherboard support SR-IOV? I couldn't really find any information online. The manual does state that VT-d is supported, but then again BIOS support for SR-IOV is required for it to work.
That board uses the C204 or C202 PCH, which I don't think can support SR-IOV on the onboard NICs, but PCIe slots 4, 5, and 6 run directly off the processor. I would try a NIC that supports SR-IOV in one of those slots.