Hey man! I have the exact same issue. Did you happen to figure out the solution?
When I install the 4k60 into the PCIe slot of my streaming PC's mobo, Windows freezes on loading upon booting the PC. Once I remove the elgato from the PC it boots perfectly fine. I was wondering if it's a PSU issue, which Im currently at 650W. I'm guessing there is some kind of power struggle, but I can't seem to find the exact amount of power the 4k60 needs on its own. My streaming pc specs are 1660 super (GPU), i7-3930k (CPU), x79 (mobo), SATA SSD, 650W gold PSU, 7 120mm fans. I also understand that my CPU is not 6xxx series i7, but that doesnt seem to be an issue when I unplug the gpu and keep the elgato in.
I tried changing 4k60 installation from PCIe x16 to PCIe x8, same problem
however, if I remove GPU from streaming PC and boot the system, elgato works just fine, but Im unable to stream off streaming PC, and if i remove the elgato and keep the GPU in streaming PC, it boots just fine and everything works, except now I dont have the elgato in my streaming PC
I ordered an 850W PSU that's supposed to arrive tomorrow from Amazon, but for some reason I'm not very hopeful right now.
I would like to know the answer to this as well. I am currently having an issue with this. From what I've read it may be an issue with the mobo and the way it reads the PCI-e slots. Anyone know what's going on?