Just dropping in to say I got this to work on my 4 year old ASUS Maximus Formula (Republic of Gamers) mobo which only supports X-fire. I have 2 x GTX 560 Ti cards. Rest of the rig is Q6700 quad core CPU, 8GB Hyper X 1066 MHz DDR2. OCZ Vertex 2 160 GB SSD.
There were a few issues, for example...