Try to buy a motherboard that was designed to mine with 6 GPUS, not a gamer's motherboard that you might be able to tweak, hack, etc to run with more then 3-4 GPUs and even then may or may not be stable. We have a couple "gaming" motherboards that work with 6-7 GPUs, but I vastly prefer the motherboards that re plug and play out of the box with 6 or more GPUs. That means you want to find an AsRock H81 Pro BTC (quite rare in 2017) or one of 3 Biostar models - TB85, B250 BTC or B350 BTC, all of the last 3 are still in production I believe.
I bought 2 B250 BTC today from a mining store but they won't be in stock until July 3rd. I didn't order the the h270, reading forums it has the same problems. I hooked my H81 BTC up in the mining rig and I got a shock from the frame, it was on spacers. Now it doesn't recognize one card and flickers constantly. I also get the error message to plug the 4 pin molex in, they are plugged. Changed everything, PSU, some cables, checked riser after riser. One GTX 1070 in pcie 0 wasn't recognized.
I think my H81 BTC might be destroyed
Worse is I was mining with one rig, now I have 12 GPU and 2 unstable motherboards and I can't mine.
