I think its possible that the 150w supply via the pci-e slot and pci-e 6pin isnt enough. 150w for all pci-e 1.1 boards. I think pci-e 2.0 boards can supply 150w via the slot and so theres 225w available.
Think about it this way, at 1.35v compared to stock of 1.15v, the power consumptiion has increased 38% before any clock increase. At 1.4v this is 48%. Say you hit 800mhz for the core, thats a combined increase of 76% and 89% respectively.
At a peak wattage of 109w
and if we attribute 80% of that to the core. A 76% increase in core power consumption is an increase of 66w. This is a peak wattage of 175w. For the 2nd scenario it would be even higher.
NB the 80% attributation to the core is a pure guess. Also, if the card xbitlabs used has a lower than 1.15v stock voltage, it would be even higher.
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