From the article:
If you are upgrading to newer processors that have more cores, but slower speeds, then your applications may run slower unless you prepare them to run across multiple processors. While compiler builders such as Codegear (Borland) and Microsoft are sure to build features into their compilers to help with this speed issue, in many ways, the onus is on the developer. It is up to developers to change the design and architecture of their applications to take advantage of the added core. Sequential applications will take advantage of a single core only; if a design change isn't made, you won't gain any speed."