We just received a Dell OptiPlex 9020 SFF and a pair of Dell U2713HM monitors. I have connected a single monitor for the time being. The maximum resolution available is 1920x1080 rather than the native 2560x1440. The monitor is connected to the add-in card (Radeon 8570, I believe) which presents what I believe to be a DVI-D port and a DisplayPort. The connection is from the DVI-D port to the monitor's DVI-D port via the DVI-D cable which I received with the machine. It is clearly labeled as a dual-link cable. How do I fix this?