I have a Radeon 7970 driving a Dell U3818DW at 3840x1600. Nice curved display that works great using DP1.2. But no boot menu. Somebody else on this forum suggested forcing Dp1.1. The regular manual had no such option, but after some googling I found the solution. - Pop the on screen menu - Go to select the input - Select DP - Hold the Check Mark button for 10s. The first time it will toggle to DP1.1, the second time back to 1.2 Confirmed getting the boot menu!