I had the same problem. The last thing I tried was to run multibeast installing everything except the hd530 driver. I set my system profile to iMac 17,1, increased the graphics memory in bios to 128MB. After this booted fine, still no acceleration, I ran multibeast again, this time only installing the hd530 driver and it worked... I don't really know why but I hope that helps. (Gigabyte z170mx gaming 5, i5 6600K)