Intel Nehalem Turbo Mode explained

One of the new features of the Intel Core i7 "Nehalem" architecture will be Turbo Mode. Anandtech published a slide which explains this technology. Basically Turbo Mode will allow the processor to boost the single-threaded performance of your system by deactivating cores and increasing the frequency of cores dynamically.

For instance, if you run a game that doesn't take advantage of multiple cores the processor may decide to turn itself from a 2.4GHz quad-core into a 3GHz dual-core CPU, thereby offering a nice performance boost while keeping the power consumption at the same level.