Dresden, Germany - The latest semi-official ranking of the world's fastest computers was a no-contest for the top spot, with the Roadrunner, a new US government computer which can simulate atom-bomb blasts, winning hands down on Wednesday.

The twice yearly Top 500 List was issued in Dresden, Germany at the annual Supercomputer Conference.

IBM announced earlier this month it had broken supercomputing's "petaflop" barrier with its Roadrunner system at the Los Alamos National Laboratory, capable of over 1 petaflops (one thousand trillion sustained floating-point operations per second).

The compilers, top500. org, said the global high-performance computing community had entered a new realm.

Roadrunner has almost double the power of the second place-getter on the list, also located in the United States. BlueGene/L at the Lawrence Livermore National Laboratory clocked 478.2 trillion FLOPS.

Modern off-the-shelf personal computers are sluggish by comparison, capable of about 8 gigaflops, or 8 billion operations per second, computer experts said in Dresden.

Third placed was followed by another US computer, Blue Gene/P Solution at Argonne National Laboratory.

The top non-US computer was JUGENE at Juelich, near Cologne, Germany, which was ranked sixth. (dpa)