According to the Top 500 Supercomputer Sites list that carries out a bi-annual list ranking the world's fastest computers, the top position was retained by IBM's Roadrunner supercomputer at the Department of Energy's Los Alamos National Laboratory, with a rating of
1.105 petaflops.

With one petaflop representing one thousand trillion calculations a second, the total combined performance of the leading 500 machines touched 22.6 petaflops - indicating a twofold increase in the year-before ratings.

In the second position on the Top 500 list announced Tuesday was the Cray XT5 Jaguar system at Doe's Oak Ridge National Laboratory, with a 1.059 petaflops rating; while the third position went to IBM's Jugene, which worked its way into the top 10 with an 825.5 teraflops rating.

Other supercomputers moving into the top 10 slot includes the Juropa; the Cray XT5 system at the University of Tennessee; and the IBM system at Lawrence Livermore National Laboratory.

The Top500 list, put together at Germany's University of Mannheim; the Lawrence Berkeley National Laboratory; and the University of Tennessee, Knoxville, showed that 291 out of the top 500 supercomputers are based in the US.

Though IBM continued to lead in terms of overall performance, Hewlett-Packard maintained a marginal lead in the number of systems in the Top500, while Intel's Quad-core processor-based systems accounted for as many as 383 systems.