A complex supercomputer being constructed for the US government has demonstrated double the power of the long-reigning supercomputing champion, despite being only partially built.

IBM's BlueGene/L achieved a record-breaking performance of 70.72 teraflops, announced Spencer Abraham, US energy secretary, on Thursday.

A single teraflop is one million million floating-point operations - or intensive mathematical calculations - per second, and is about 100 times faster than the most powerful desktop computers.

The new speed by BlueGene/L is precisely twice as fast as the computer officially ranked the world's fastest - NEC's Earth Simulator, based at Yokohama, Japan.

BlueGene/L has been developed in cooperation with the US department of energy's National Nuclear Security Administration and is being constructed at Lawrence Livermore National Laboratory, California.

Chart success

The official list of the 500 most powerful supercomputers in the world will be revealed at the Supercomputing Conference 2004 (SC2004), in Pittsburgh on Monday.

The Earth Simulator currently occupies the number one spot with a peak performance of 35.86 teraflops. But now BlueGene/L seems destined to storm straight to the top of the chart.

Known as the TOP500, the list is compiled by a handful of supercomputing experts using an industry standard software benchmark called LINPACK. It is published twice a year.

NEC's grip on the top spot has seemed increasingly precarious as several companies have claimed to possess the world's fastest computer in recent months.

Custom-built components

In September 2004, IBM revealed that an earlier prototype of BlueGene/L had recorded 36.01 teraflops. Then, just a month later, NASA announced that a new supercomputer called Columbia, built at Ames Research Center in California, had managed 42.7 teraflops.

But BlueGene/L may come to dominate the Top500 list for some time. It has been designed to include an unprecedented number of different processing units - 65,536 in all - and is expected to reach a staggering 360 teraflops when completed. The Earth Simulator has 5120 processors and Columbia has 10,240.

Unlike many leading supercomputers, BlueGene/L is made from custom-built components. In contrast to the earliest custom supercomputers, however, BlueGene/L is also designed to be modular and highly scalable so new modules of processors can be added on without losing efficiency.

But it remains to be seen just how stable the system will be once completed. Among its ultimate tasks, the completed version of BlueGene/L will be used to carry out complex simulations designed to assess the condition of ageing nuclear weapons.