Dual core vs. Single core - Buying a New Laptop

Q: Will a single-core 2.0GHz CPU perform faster than, say, a Core Duo 1.86GHz CPU?

A: Unfortunately, it’s not that simple. The performance depends on the type of application and how it was programmed. In order to take full advantage of the dual-core platform, the program must be written to permit multithread processing.

But even for single-thread applications, the faster 667MHz font side bus speed of the Core Duo chipset may give it an advantage over the older 533MHz FSB platform if the program involves frequent data transfer. However, for single-thread number crunching tasks, a faster single-core processor may trump a slower dual-core chip. Link.