Today I tried to get the Dell to show 5K. It should boot from the 4K 1x DisplayPort, that works, but how to get the 5K? Without the 1x DisplayPort (4K), the Dell boots too, from the double Displayport cable set, but it shouldn’t do that. And only 4K 3820x2160. The client brought his MacBook, that showed the 5K. I think the 2x Displayport cables could be the culprit. There is very little information to be found online, so I hope there’s somebody here who knows more than I do.