will stock fan do the job good if i overclock 6800gt to ultra speed 400/1100? or i will have to buy more fans?
Should be fine (sorry to echo). 6800GT's use lower voltage than 6800ultras and this is why they need lesser cooling and power. However (most importantly) this doesn't prevent them hitting 6800ultra speeds and because they have all 16 pipes by default you get full 6800ultra perf at the same clock speeds. In effect you get a card superior to a stock 6800ultra because it's smaller, cooler and less power mad! However NOTHING is guaranteed when o/c'ing, although initial 6800GT results are incredibly encouraging. You'll have to o/c in the usual way, small steps and throughly test each time. If you get 1% or 50% faster by o/c'ing it's something for nothing ... well okay something for the sake of your warranty!
