Hey, I've got HWMonitor and CPUZ set to load at start up, idle temps of the CPU are 19 - 25c depending on ambient temps (live in Uk) load temps whilst running real bench, max out between 65c and 70c

I'm nigh on 99.9% sure its not a temprature issue due to the fact, if I yank the second GPU, running the rig on just one of the 1080's (doesnt matter which) the system works happily, all day every day.

Also I dont believe the extra GPU appears to put any extra load on the CPU specifically, if it does, voltages, temps dont appear to show any difference. Now as for the PCI Lanes which are full, well thats a different story.

It's a weird one that's for sure, and at the moment I'm running my shiny new machine minus one of its £600 components, which is abit frustrating.

I'm gonna run some more tests over the weekend, but I think its heading towards me replacing it with a more competant motherboard. Thinking either the Alpha or Extreme. Utilise the Hero in a smaller less demanding setup.

So following a weekend of rigorous testing, think the issue lies with the motherboard, can’t explain it otherwise.

I've ruled out temperature, for two main reasons, running the rig with the side panels off, in my offices comms room has the entire rig running at a frigid 17c and 28c maximum under load. Also if the rig is left in a powered down (soft off) state overnight and you turn it on next day (so powered down for several hours), it will load with the CPU throttle locked to 800Mhz. If I was to flick the rocker or disable c-state, ErP modes it boots just fine. However as stated before, it'll throttle lock to 800mhz anywhere from a few minutes after boot to several hours. Other issues I've noted is just a general shaky level of stability, USB devices disconnect and reconnect randomly when two cards are installed, exiting 3D applications, sometimes cause the system to freak out and grind the desktop to a crawl.

The only common theme, is that if I yank that second GPU, the entire system operates normally, in fact id even go so far as to say it’s faster, smoother.

In summary though, with a second GPU installed, it doesn’t appear to matter how or what I try, it eventually flakes out. Be that the system with just two GPU's and nothing in any other PC Slot, running one 16Gb dimm as opposed to two, or running with optimise defaults or customised settings in the BIOS.

The fact from a soft off boot it will without fail, every time, lock to 800mhz even if the CPU temp never went above 20c from cold boot - but I do the same with one GPU its fine, after all my testing the only thing I can think, is there something iffy with the board, but it only appears when it's asked to run two GPU. So I'm thinking maybe the best course of action is to replace it with a different series, was thinking trying the Sabretooth Mark 1 unless anyone has reason to avoid that board. I dont see a reason to RMA the VIII Hero board when I can utilise it elsewhere as long I ensure I dont use it for SLI. Just hope this finally resolves the issue. Because after replacing the PSU (after thinking it was a power issue) trying everthing I can think of, I'm getting abit tired of it now.