I am also having the issue of being unable to run 2x 2080 Ti cards in my system. I can use the dip switches to disable a PCIE slot of either card (which are plugged into slots 1 and 3 of the x16 slots) and it boots fine. Previously I was running 2x 1080 Ti with no problems.
This issue is not plaguing other manufacturers x399 boards so is not an AMD related issue. I've also been posting on overclock.net
https://www.overclock.net/forum/11-a...thread-96.htmlelmor has said he will test tomorrow so hopefully he has an answer for us in the next few days.
I've raised a support ticket with ASUS Technical Support and completed the Zenith Extreme bug report form. Knowing that I am not the first to do this and not seeing replies elsewhere makes me wonder if this issue is being taken seriously by ASUS. This is a high end motherboard that costs a not inconsiderable amount and the support has been rubbish.
I was on the edge of loosing hope until the reply from elmor, to which I am very grateful to him for. He has restored a little spark in me for the time being.
The problem was, as far as I can see, first raised by eco_batch on 22.09.18
https://rog.asus.com/forum/showthrea...-Load-VGA-BiosTwo full working weeks have passed and to date no official response. It's a real kick in the balls.
Unlike Harley2000 I am not sorry for posting here. There has been plenty of time for an official response to be issued and still we sit here in the dark.