Intel showed off a Core 2 Extreme processor running at 3.5GHz at a presentation:
Sources told TG Daily that Core 2 Extreme is capable of breaking the 4 GHz barrier, while it is unclear, if off-the-shelf dual-core Core 2 processors (Conroe core) will ever reach that level as the quad-core desktop processor "Kentsfield" is on track to debut in Q1 2007. Intel today confirmed that Core 2 Extreme will launch with 2.93 GHz/FSB1066 next month and will be available with 3.2 GHz by the end of the year. At a presentation today in Santa Clara, Calif., the firm also demonstrated an overclocked version 3.5 GHz that, according to Intel, offers "impressive performance."
3.5 GHz and more may not be an unrealistic level for overclocked Core 2 Extreme processors - in fact, the processor may scale very well beyond that right from the start and without any extreme cooling requirements.