PC Stats has posted an article about the technology behind Dual Core CPUs

Dual-core processors work pretty much as you'd expect them to. At their most basic, both Intel and AMD have taken two mostly (or in the case of Intel, fully) functional processor cores and joined them together in a single processor die. Each core functions and processes data independently, and the two are co-coordinated by the operating system software. In this article, PCSTATS is going to focus on both company's versions of this technology, how it works, and the kind of performance boost you can expect from it. Currently only certain of AMD's Opteron server-class processors are available with dual cores, but very shortly AMD will release the Athlon 64 X2 line of dual-core desktop processors. Intel has taken the opposite approach, already releasing the 'Pentium Extreme Edition 840' desktop dual-core chip, while its 'Pentium D' and dual-Xeons lines are not far behind.

The Technology Behind Dual Core CPUs