This is it: the world's fastest supercomputer. Roadrunner took over the top spot in June and was able to fend off a stiff challenge from the Cray system at Oak Ridge. In addition to being the world's fastest, it's one of the most energy-efficient supercomputers on the Top 500 list, requiring fewer than half the kilowatts used by the world's second-fastest supercomputer. Using x86 processors in conjunction with the same chips used by the Playstation 3, Roadrunner ensures the safety and reliability of the nation's nuclear weapons stockpile and is also used for research in astronomy, energy, the human genome and climate change.