A Cray supercomputer at the US government's Oak Ridge National Laboratory was named Monday the world's fastest, overtaking an IBM supercomputer at another American research center.

The ranking released by researchers from the United States and Germany found that Titan, a Cray XK7 system installed at Oak Ridge in Tennessee, achieved 17.59 petaflops, or quadrillions of calculations per second.

Titan, which gets funding from the US Department of Energy, is used for research in energy, climate change, efficient engines, materials and other scientific research.

Titan knocked the IBM Sequoia at the Lawrence Livermore National Laboratory in California into second place. It could only manage 16.32 petaflops.

Rounding out the top five were Fujitsu's K computer at the Riken Advanced Institute for Computational Science in Kobe, Japan; an IBM BlueGene/Q system named Mira at the Argonne National Laboratory in Chicago, and another IBM BlueGene/Q system named Juqueen at the Forschungszentrum Juelich in Germany.

Researchers said 251 of the 500 systems were in the United States, with 105 in Europe and 123 in Asia, including 72 in China.

Intel provided the processors for 76 percent of the systems while AMD was used in 12 percent and IBM in 10.6 percent.

The announcement came from the TOP500 list compiled by the University of Mannheim, Germany; the Lawrence Berkeley National Laboratory and the University of Tennessee.