What the top temp is I can't say, but I do know that anything much over 55c and performance is impacted.
the best mix for overclocking/performance is FSB/Multi. the more you push your FSB the better performance you will get. Keep your RAM in even dividers, (1:2 or 1:4) odd dividers (1:1 or 1:3) really hurts the performance, even if the RAM is faster at 1:3.
4.2 is a great OC, but for day to day activities, I ran my 965 at 4.0.........
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