I just built a new PC (first one) with an MSI Radeon RX 480 and FreeSync monitor. When I plugged in the Displayport cable to both the graphics card started making a clicking noise. This happens with the power cable removed from the computer and doesn't happen with HDMI. I haven't used Displayport before and none of my other devices support it so I can't check it on another machine. The card is working as far as I can tell, I haven't launched a game with it yet (in the process of installing everything still) but it appears to be working with the latest drivers and I was able to turn on FreeSync just fine.