Behold the power of math:
1: A64 Venice, at 2.4Ghz maxes out at about 60watts (according the Xbit's testing). Bumping up to 2.6Ghz, and assuming a bit of an OV, you're probably close to 70watts, max.
2: In our testing of the XP90
, using a 92mm Nexus fan at 12, 7, and 5 volts, we got °C/W's of 0.28, 0.33, and 0.41, respectively.
3: Doing the math for your CPU, assuming a 30° case interior temp:
With the 92mm you can expect a max CPU temp of 50° at 12v, 53° at 7v, and 59° at 5v.
In other words, even running the nexus 92mm fan at a measly 5 volts will still provide plenty of cooling for that overclocked CPU.
That's why we put °C/W numbers in reviews. Isn't math neat?