Our expectations were exceeded when trying to overclock the Core i5 661 which didn't mind getting pushed from the stock 3.33GHz to 4.60GHz using air cooling. This result was achieved using the Cogage TRUE Spirit heatsink, which had no trouble keeping the 32nm processor cool, even at such an extreme frequency.
This impressive 38% overclock was achieved by increasing the base clock to 177MHz, with the clock multiplier set to 26x. With 1.425v of power being fed to the processor, we arrived at a completely stable 4.6GHz overclock. In other words, users shouldn't have any problem pushing their Core i5 661 processor to 4.0GHz.
The overclock boosted the Core i5 661 performance in the CINEBENCH R10 multi-threading test by 34%, which was enough to surpass the quad-core Core i5 750.
Despite the huge gains seen in CINEBENCH R10, we saw a more moderate performance increase in WinRAR.