The aforementioned details were made public in a recent post on Asian hardware site Xfastest, which included 3DMark Vantage scores and results from the suite of CPU tests in Everest Ultimate Edition. Tests were performed using a reference Intel motherboard, where the 2.66GHz Core i5 part seemed to yield better results than a Phenom II X4 955 running at 3.2GHz.
The Phenom II X4 955 currently sells for around $245, while the Core i5 is expected to cost $196. Performance differences weren't that large, though, and seeing that these are the first benchmark results made public, we should probably hold judgment until we can perform our own tests or a more thorough review of the chip is leaked online. Also, by the time Intel officially takes the wraps off its Core i5 processors, AMD is expected to have several new 45nm quad-core models in the market.