Hi Florian ,
I have a Sapphire 7950 dual x , and I see you have a Sapphire 280 Vapor X which I find very similar as layout design and model. I am using 10.10.5 with latest Clover on a Z77-D3SH v1.1 and i7 3770. I can boot without problem with my 650 Ti boost and igpu, but every time I put my 7950, I get a flash and reboots at IOBluetoothHCIController with is graphics related. I've tried all possible combinations and personalities I can't pass that flash.Card is recognized in Clover as 7950/280. I've tried on a fresh install of 10.10 and the same so I think is a BIOS trick or is something I'm missing. Can you help me please? I've checked all tutorials but still no luck. I've attached my config I've tried so far.
Thank you!