I had issues with my 670s a while back wheen they were running in PCIe 3.0 mode; try changing in BIOS to PCIe 2.0 and see how that helps you.
As mentioned prior motherboard only supports up to pcie2.0.
I'm slowly working through testing all my ram (I really have 16gb but only use 8 usually due to one set definitely having a faulty stick). One stick from each 8GB set passes 8 with 0 errors. Just testing the other two now... If they both error then I'll know the kit I was using had a faulty stick. Currently asking corsair about RMA'ing.
