IBM's Roadrunner, which provides more than 1 quadrillion calculations a second for nuclear security and scientific research at the Los Alamos National Laboratory, topped the list Wednesday of the world's 500 fastest computers. The supercomputer also was found to be one of the most energy-efficient systems.

IBM also grabbed the No. 2 and No. 3 slots in the Top 500 list with the Blue Gene/L system at the National Nuclear Security Administration's Lawrence Livermore National Lab in California and the Team Blue Gene/P system at the Department of Energy's Argonne National Lab in Chicago, respectively. The biannual list was released at the International Supercomputing Conference in Dresden, Germany.

The $100 million Roadrunner, built by IBM and scientists at the NNSA-run Los Alamos in New Mexico, gets its muscle of 1.026 petaflops from 12,240 IBM PowerXCell 8i chips, which handle the math-intensive calculations. For all other chores, the machine uses 6,562 Opteron Dual-Core processors from Advanced Micro Devices. The PowerXCell chips are derived from the same processors that power Sony's PlayStation 3 video game console.

The Roadrunner, which is based on IBM QS22 blade servers, is more than twice as powerful as the Blue Gene/L system, which held the top spot in the last list, released in November. That machine clocked in at 478 teraflops, or 478 trillion calculations per second. The No. 3 Team Blue Gene reaches 450-teraflop performance.

Rounding out the top five systems was the new Sun Microsystems' Sun Blade x6420 Ranger system, at 326 teraflops, and the upgraded Cray XT4 Jaguar, at 205 teraflops. The Sun system is at the Texas Advanced Computing Center at the University of Texas, and the Cray machine is at the Department of Energy's Oak Ridge National Laboratory in Tennessee.

The remaining top 10 systems, respectively, were the IBM Blue Gene/P system at Forschungszentrum Juelich in Germany, the SGI Altix ICE 8200 at the New Mexico Computing Applications Center, the Hewlett-Packard Cluster Platform 3000 BL460c at the Computational Research Laboratories in India, the IBM Blue Gene/P at IDRIS in France, and the SGI Altix ICE 8200EX at Total Exploration Production in France.

IBM had 210 systems on the list, the most of any supercomputer vendor. HP, however, was not far behind with 183 systems, including the No. 8 system.

Among all the systems, Intel processors were used in 75% of the machines, up from 70.8% in November.