I went through a similar experience yesterday when I attempted to install two Sapphire Fury X cards in crossfire. The driver installation works totally fine with a single card in any of the PCIE slots I have, but the moment I add another card, driver installation would hang/freeze/cause display signal to be lost about half way into "Installing Display Driver" after a few on and off black screens. I ran into the same problem with both 15.7.1 and 15.9.1 drivers that are currently available. I wasted an entire afternoon on this thing, but somehow I managed to get crossfire to work by doing the following:
- Install the first card into the top PCIE slot and install the driver
- Pull out the first card, and install the second card in a different PCIE slot and install the driver
- At this point, there should be no errors.
Add the first card back and restart the system - Windows should notify you that no drivers are available for your Fury X. Install the graphics driver again, but this time, the system will hang fairly early into the installation process. I then restarted the system and both cards worked for me afterward. The only downside right now is that I cannot disable crossfire, or the system hangs. I think the same goes for enabling the crossfire. Luckily the crossfire is enabled by default and I've tested it in a few games as well as Firestrike 3Dmark with no error so far with roughly 66 degrees Celsius under load.
I hope a fix is in the works soon from AMD. This has been such a terrible experience for me. Having come from 2x R9-290x, I know that my system is powerful enough to take the load of two fury X. I am very happy once I get the cards to work, but there's no reason people should have to go through such a convoluted way to install crossfire after shelling out over $1300. R9-290x crossfire never gave me any issues.