With performance almost double that of the Earth Simulator, in Yokohama, Japan, IBM's Blue Gene/L is officially the world's fastest supercomputer.

The Top 500 supercomputers bi-annual list was officially unveiled in the States last night, and IBM walked away with four of the top ten machines.

Blue Gene/L is a 33,000-processor prototype of a much larger $100 million system that will be delivered to Lawrence Livermore National Laboratory in Livermore, California, during the first half of 2005. The system is capable of performing 70.72 trillion calculations per second, making it the first new system to top the list since the Earth Simulator first appeared in 2002.

When fully assembled at Lawrence Livermore, Blue Gene/L will be a 130,000-processor system with an estimated peak performance of 360 teraflops, according to IBM. A teraflop is one trillion calculations per second.

In second place comes the 10,240-processor "Columbia" supercomputer, built by Silicon Graphics(SGI) for the NASA Ames Research Center in Moffett Field, California. With a benchmarked performance of 51.87 teraflops, it easily beat NEC's Earth Simulator, which was measured at 35.86 teraflops.

Virginia Polytechnic Institute and State University reappeared on the list, finishing in seventh position five months after dropping off the June list because of a hardware upgrade to Apple's Xserve systems. Virginia Tech's "SuperMac" system reported a benchmark of 12.25 teraflops.

The Top500 list is compiled from results that are voluntarily submitted by owners or manufacturers of the various machines. It is based on the Linpack benchmark, which gauges the speed with which the systems can run certain mathematical operations.

Though Linpack is sometimes criticised for not being a universal indicator of overall performance, a high ranking on the Top500 list is highly coveted, and computer makers have been scrambling to outdo each other with benchmark results over the past few months, in anticipation of Monday's release of the list.

In September, IBM released numbers showing Blue Gene/L to be slightly ahead of the Earth Simulator. A month later, NEC announced plans to build a 65-teraflop supercomputer in December of this year. That announcement was followed by preliminary Linpack results on the SGI system, which put it ahead of both Blue Gene/L and the Earth Simulator.

Despite the unusual amount of jockeying between vendors, the Top500 list has essentially become a "two-player game" in recent years, said Erich Strohmaier, a computer scientist at the Lawrence Berkeley National Laboratory, in Berkeley, California, and one of the maintainers of the list. With 216 IBM systems and 173 built by HP, the two companies have built more than 75 percent of the systems on the list, Strohmaier said.

And while the majority of systems on the list are built in the US, the number of Top500 supercomputers being built in Asian countries is rising steadily, Strohmaier said. China, for example, had 17 systems on the list. "That is substantially up from nine systems a year ago," said Strohmaier. "It was only a few years ago that we had the very first Chinese system."

The highest European supercomputer was number four, is found at the Spanish Ministry of Education and Science, and was only introduced on Friday last week. "MareNostrum", again built by IBM, employs a cluster of 2,520 eServer BladeCenter JS20 systems running Linux and is the first top-10 supercomputer that uses blade server technology.

The two nearest UK entries were at 11 and 12, and both of them are at European Centre for Medium-Range Weather Forecasts (ECMWF) based in Reading.