All i7s that Apple uses are 4 core except for those in the 13" Macbook Pro. However, not all i7s are the same. Newer machines have Intel's new Sandy Bridge processors, which are known for being significantly more powerful and less energy expensive than the first generation Core i series processors. However, I don't think that Apple currently sells any first generation i series processors. (Someone correct me if I'm wrong, I haven't been keeping too up to date on the Mac processor scene as of late)