I'm running Gigabyte Z87X-OC mb with Gigabyte R9 280X GPU's.
Am running 4 GPU's on each MB successfully under Windows 8 using 16x slots, half on powered 16x - 16x risers, half directly on the MB.
However, I am not having any luck running a GPU on the 1x slot using a 1x to 16x powered riser. Have also tried using with and without the presence jumper. Fans on this GPU spin up, but its not showing up in Windows Device manager or in CGMiner.
Any advice on this would be much appreciated.
Will pay .025 BTC to the first person that can provide me a solution to utilize the 1x slot using my current hardware and Windows 8.
How did you hook up the jumper?
I would recommend the guide below (Scroll to the bottom):
http://www.gobitgo.com/articles/1001/How-To-Correctly-Use-and-Install-PCI-E-Riser-Cables/Good luck!