Features and benefits of dual quad core processors?

A dual core processor has two cores (eg, AMD Phenom II X2, Intel Core Duo), a quad-core processor contains four cores (eg, AMD Phenom II X4, the Intel 2010 baseline which includes three levels of quad-core processors, see i3, i5 and i7 Core), a hexa-core processor contains six cores (eg, AMD Phenom II X6 Intel Core i7 Extreme Edition 980X), a processor octa-core contains eight nuclei (eg, AMD FX-8150). A multi-core processor implements multiprocessing in a physical package. Designers can core partner in a multi-core device or freely. For example, the nuclei may or may not share caches, and can implement message passing or shared memory between the main methods of communication. Common network topologies include bus interface cores, ring, two-dimensional mesh, and the crossbar. Homogeneous multi-core systems are only identical nuclei, heterogeneous multi-core systems have nuclei that are not identical. As with a single processor system, the nuclei in multi-core systems can run such as super scalar architectures, VLIW, vector processing, SIMD, or multi-threading.

Advantage
The proximity of multiple CPU cores on the same chip allows cache coherency circuitry to operate at a much higher clock speed than is possible if the signals have to travel outside the chip. Combining equivalent CPUs on a single chip significantly improves the performance of cache snoop (alternative: Bus snooping) operations. In short, this means that signals between different CPUs travel shorter distances, and therefore the signals degrade less. These high quality signals allow more data to be sent over a period of time,since individual signals can be shorter and need not be repeated too often.
The greatest increase in performance is noticeable in the improved response time during the execution of processes CPU intensive, such as antivirus scanning, ripping / burning media (requiring file conversion) or searching for files. For example, if the automatic virus-scan runs while the movie is being observed, the application running the movie is much less likely to be under powered processor, as the antivirus program will be assigned to a different processor core running the movie playback.