Out of desperation I did "upgrade" to Win 10 to ensure that Win 7 wasn't the issue with the 6 gpu's and Win 10 did not fix the issue I was seeing with the Nvidia cards. I can say that I have this exact same mobo, cpu, memory, ssd, psu combo working fine with 6 AMD gpu's for a different rig. So I know this combo is capable of running 6 gpu's. So I am not sure what the real issue is... I thought it might be drivers issues. The other rig that I spoke of is running Linux, so there is a different OS in the mix.
When I discovered one of the GPU's wasn't being seen by the Nvidia software I then pulled it out of the mix, and I could finally get the system to boot reliably and behave normally, but still when running ccminer it would fail and crash saying cannot validate to CPU.
So if your hoping that Win 10 is the magic bullet like I was I wouldn't hold my breath. The only reason I went this route with windows on this rig was the intention to buy SP_ private release. Otherwise I would have stuck with Linux. So now if I run into any Windows related issues with the AMD cards I will just reconfig the rig with Linux and call it a day.
I hope someone is able to figure out what the issue is. Nvidia cards are more efficient than the AMD cards and I would love to have a rig that takes me in a more efficient direction for the long haul.
Windows works and the drivers work so it's time to move on.
Start from the begining and try to get one card stable when mining. If you can't get any card working
with different combinations of slots and risers you have a bad mobo or PSU.
If you can get one card working, try a second card and repeat the process with two cards. Make note of which
combinations of slots, GPUs, and risers are known to work.
If you run in to probems along the way swap the suspect card and riser with a known good combo from another
slot. Then observe if the problem changes in any way Is the known good card/riser eorking in its new slot?
Is the suspect card/riser still not working in the slot you know is good?
Keep doing that until you've isolated the suspect card/riser combo, a suspect mobo slot or just the number of cards.
If it's the number of cards it could be the mobo or PSU. Even if it's rated high enough it may not be working properly.
If you've isolated to a PCIe slot, it's definitely the mobo. It's up to you what you want to do about it.
If you've isolated it to a GPU/riser combo them swap the riser with another card to isolate the problem.
And you're done.