The Quad-Core Opteron processor was recently unveiled by Advanced Micro Devices. The new chip is designed to be more energy efficient; it can turn off unused parts of the processor, and independent dynamic core technology allows each of the cores to run only as fast as needed. For more ways to inccrease your computer's energy efficiency, visit The Responsible Purchasing Guide for Computers.
The processors are currently aimed at data centers, but AMD will release a different class of quad-core processors for desktops later this year. Early adopters of the new chips include Rackspace, Lucasfilm, and Rackable Systems.