I can see the Bios boot up UI but after that, i got signal but no video. I tried to plug only one card into the 16x Slot but I got the same result.
I had to flip the setting back to onboard card to be able to boot win again.
EDIT: it was working with one card previously but the card was directly plugged into the mainboard (that is why i was wondering if I needed a full 16x to 16 riser)
For all of my H81's I use onboard video, so I don't think that is an issue (but with the Anniversary I had to go to the GPU). I also run Win10 without running any special mods, I basically do a clean install, install the drivers for the H81, and then the latest ATI/Claymore. In the instances where I did have an issue with the boards, it typically was power-related, so you might want to doublecheck your risers, etc.
And on the Win10 licenses, I don't buy any - it mines fine without a license, and I just disable automatic updated with gpedit. There aren't any legit licenses for Win10 that aren't in the $100 range - if so you're just paying for pirates stuff (like a shared key, etc), don't bother.
Thanks for info.
I have an extra riser, i will try that
So, I plugged another card into the slot 6 (which was the card in problem in win 7) with the card 5. Everything works fine ... I unplugged card 5 and card 6 is working.
So it's a win 7 problem.
Will work on that ...
EDIt: All my riser are powered by a single PCI-E cable ... do I still need to plug the molex on the MB ?
EDIT: Not sure what to do next except to switch to win 10 ... I use Claymore 16.9.1. with the 6 GPU mod ... I got 7 GPU in fact with the onboard card. So i don't know... So close but so far !