There are no drivers for that series of cards and Win8.1.
Radeon Product Compatibility
Radeon Software Crimson ReLive Edition 17.4.4 is compatible with the following AMD Radeon products.
Note that AMD Radeon™ R9 Fury, Radeon™ Pro Duo and Radeon™ RX 400 Series are only supported by Radeon Software Crimson ReLive Edition on Windows 7/8.1/10 64-bit. AMD Radeon™ RX 500 Series graphics are only supported by Radeon Software Crimson ReLive Edition on Windows 7/10 64-bit.
Thx for pointing to the obvious.
The followup question would be how AMD can ignore about 10% of desktop gamers and not release drivers for the second newest os version more than a week after starting to sell the new generation of gpus.
I used NVidia cards for a long time now and thought I'd give AMD a chance on my secondary rig because of the latest price policy of Nvidia. Guess what? Both rigs run on Windows 8.1. I didn't even think about checking for drivers before purchasing, because that would be something so basic that no company can ignore the last os versions, right?
Well, seems like I learned something today. I'll wait till Monday for drivers and will return the card afterwards and switch back to NVidia. At least I don't have to wonder aout the samll marketshare of AMD GPUs any more...