On that motherboard, you'll have to go into the bios settings and disable the onboard graphics to enable the pcie slots. Yes it sucks not being able to use the onboard graphics especially with a gpu mining rig. I don't know if it's a design flaw or a batch of bad boards but I had the same issue with the same board.

If you are planning to use SMOS , you can ssh into the rig without connecting a monitor or you can view the rig in real time on their website/your rig list page . You only need to connect a monitor for the initial setup of your system, afterwards you won't need it to be connected to your GPU. Chris B.