Haha, still sounds like a plausible explanation. Have you at all tried and observed similar behaviour. In hindsight I wish I checked their with all my prior Fiji based cards also.
I have to a very small degree, all I noticed was a very slight drop in performance in Heaven benchmark. I've seen this sort of thing happen many times before on earlier cards, mainly AMD ones. Its as if the card is being pushed too hard without compensating with higher voltages for stability and it starts to fall over itself trying to keep up with the settings. Obviously increasing voltages increases heat output and in the case of the Nano, throttling starts if temps get a bit high. Conversely, if voltages are kept at stock to keep heat down, and clocks are increased, then it'll start to fall over as it needs the extra voltage to keep going.
Again, this is pure speculation on my part, but kinda based on what I've seen in the past.
I think with the Nano, the user has a fairly "narrow" bad of setting ranges to work with and its a case of finding the "sweetspot" wether water cooling or air cooling.
Thats my take on it anyway and other user's results will differ as all cards are different and some are just "better" than others.
Myself, I just wanna make it quieter using air cooling and see what I can get out of it as I'm really impressed with this gpu considering it's size/performance ratio. I also like tinkering and trying other things out, hence me wanting to try a larger fan, 120mm.
![Smile :) :)](/styles/default/xenforo/vbSmilies/Normal/smile.gif)
It also means if I ever decide to chang me case for a lot smaller one, I shouldn't have too much bother accommodating the Nano.