Right now, Intel has no real options to fight AMD in the single core arena. Though the Pentium 4 Prescott might be capable of running at 4 GHz, this would only be a clock speed increase of 5% when compared to the 3.8 GHz of the 570 and 670 models. This small clock speed increment would not make much of a difference.
This is why Intel is focusing on its dual core Pentium D and Pentium Extreme Edition chips. While the Pentium D, based on the Smithfield core, merges two Prescott-type Pentium 4 cores, the Pentium Extreme Edition is exactly the same but with Hyper Threading enabled. Traditionally, the Extreme Editions are priced at $999 and target enthusiast users and gamers who have virtually no budget limits.
We consider the dual core Pentium Extreme Edition to be quite an amazing product from a technical point of view. Two cores with Hyper Threading enable as many as four logical processors to operate simultaneously, and the more applications you execute at a time, the more Hyper Threading will help you. But this provides hardly any advantage for gaming, which is the market that the Pentium Extreme Edition is targeted towards.
The Pentium D is different. While the three versions from 820 to 840 run at between 2.8 and 3.2 GHz, their pricing is very attractive when compared to the fast single cores or to AMD's dual core Athlon 64 X2 in particular. With a decent percentage of applications already being thread-optimized, Intel is now trying to establish a large basis of dual core systems by accelerating Pentium D sales at attractive prices.