Think about this: It goes up to 5000+ rpm when the core temp gets close to the threshold.
Replace the whole stock cooler with either Silent 775 from Thermaltake or the Zalman Cu7700/7000. They give you lower temps and less noise. I tried both and the Zalman was even quiter with its 2000 top fan speed. But Silent 775 cools better with a tiny bit louder/faster fan spin.
I'ts not just you. I listened to one at the local computer store, and had no qualms whatsoever on spending the extra $$$ on the Zalman 7700cu. My stock cooler is still in the box, with a virgin thermal pad. Overclocking or not, I have no need for horrenously loud fans, which is why I have 4 120mm fans in my tower that are all 2000 RPM or less. Tho the Zalman @ 2000 RPM is noticable, just not a dustbuster.
Stock cooler actually gets the job done. it most likely keeps the temps under control but not a good control. Considering the dimention of the the stock heat sink being significantly smaller than, say the Zalman 7700Cu, it needs a high speed fan to compensate. Since the core temp could easily get to a ridiculous high point, The fan has too spin like crazy to prevent the chip from burning. Im using Slient 775 plus the Vcore control to tame the heat.
What a difference!
What kind of temps are you getting with the stock cooler? I was using a gigabyte 3D Cooler cause it was the only 775 hsf I could get at a local store and my temps were around 39-42c idle. My experience with the new E0's is that they run way cooler. My 478 prescott had about a 10c higher idle.