In general it is recommended to have it plugged for SLI and the board circuit will draw power as and if needed. Now for the crashes, it is very hard to say what's the reason behind. First try to stress the system with your GPUs at default settings and without your manual "touch". Also I don't know how loaded is the rest of your system. 2X670, sure is not 2X570. 670 draws less power, but if you OC everything and you have lots of HDs, fans or cathodes, maybe your PSU is not enough.
jsarver wrote:
im running sli. the cards dont crash on benchmarks (overclocked or stock) or stress tests but i seem to run into issue with long gaming session (battlefield 3, crysis 3) and again it only happens very randomly. its hard to narrow down an exact factor that causes the crash. this is only while I'm over clocked. i know obvious answer is turn down oc but im hoping that a little more constant power might fix this...
If the crashes happen only under OC and after long gaming session, I would say that the problem is focused more on overheating issues. Suspects can be your PSU and VRMs or Memory of your GPUs. Maybe it's time to step down the clocks a bit to let them breath. The benefit will be huge and your loss in FPS will be minimal. For the wiring, I always use and suggest to use all lines (12 Volt rails), to distribute the load of the PSU, to as much as possible lines. If you use only a couple with extensions to light up everything in the box it's easy to have a single 12 V line overloaded.
