http://www.wordiq.com/definition/Cache
If you are trying to decide between a Northwood and Prescott P4, the extra cache in the Prescott is counterbalanced by the shorter pipelines in the Northwood, so it's a wash. The Prescott runs a lot hotter than the Northwood, and the only real advantage to the Prescott at this time is its higher overclocking ability. If you don't plan on overclocking, stick with the Northwood.