I just got 2 Vega 64s and installed them in my system. It seems to cause nothing but problems. I reinstalled windows and it seemed to work better for a while. Games ran very poorly until I switched the ddr bank interleaving from auto to channel. I was happy. Everything was going great. I started installing a bunch of games and then the system just ground to a halt. No matter what I do the system is "working" but unusably sluggish. (like mouse will move every couple of minutes. I've tried everything I can think of and it all seems to center around the hard drive being accessed. System works in safe mode but any number of applications running is enough to slow it to a halt. Removing one video card completely fixes the problem. When the system is being sluggish I also get alerts from raiXpert2 that an array has been disconnected and then inserted. It feels like there are not enough resources of some sort but I havn't been able to figure out what. I have tried different settings for the PCIe slots switching unused ones to NVME raid mode. I figured I would check here in case I'm just doing (or not doing) something really stupid before I give up and resign myself to only having one awesome GPU.
Asus ROG ZENITH EXTREME
Amd Threadripper 1920X
Corsair Vengeance RGB LED 32GB (4x8GB) DDR4 3333 (PC4-26600)
Corsair AXi Series, AX1500i, 1500 Watt (1500W),
Samsung 960 PRO Series - 512GB PCIe NVMe (3 of them set up as a raid 0 boot drive)
ROG STRIX RX Vega64 8GB OC (1 or 2 depending on if I want to actually use the computer. LOL)