Set Powertune to a lower level, this helps to run more stable.
Powertune is set to zero on all four cards. I don't think the 5xxx and 6xxx GPUs have the powertune option.
Sam, it's been running for about 12 hours now without a hiccup, so I think it will be okay for now. I am getting some HW errors on GPU3. None on the rest. Should I be worried?
In my experience HW: errors eventually lead to system destabilization so I would lower the clocks by 5Mhz increments until the stop. If your temp on that GPU is OK, around 75c or whatever your temp target is it should be OK though.
But I'm still baffled as to why you can't raise intensity to 8 or 9 on the none display GPU's.