Japan's Marine Science and Technology Center's Earth Simulator remains the world's most powerful computer, according to the latest version of an industry ranking, but for the first time a serious competitor has made an appearance.

The NEC-built Earth Simulator has been at the head of the biannual Top 500 Supercomputing ranking since June 2002 and its 35.9Tflops (teraflops) maximum performance rating has kept it at that position in the latest chart, which was released on Sunday. But its days at the top appear to be numbered.

One machine missing from the latest ranking was the cluster of 1,100 Power Mac G5s, built by Virginia Polytechnic Institute and State University. The machine achieved a maximum performance of 10.3Tflops to rank third in the previous chart. This time the machine didn't make the list because it was out of service for hardware upgrades, said the ranking authors.

Two prototype versions of IBM's Blue Gene supercomputer have made the top ten and the authors of the ranking say they expect the final version of the computer to become the number one machine by this time next year or possibly late this year.

Even by the standard of today's supercomputers, Blue Gene will deliver an awesome amount of processing power. The first system will be installed at Lawrence Livermore National Laboratory in California and is expected by IBM to operate at a peak performance of about 360Tflops – or nine times the NEC machine's peak performance of 40Tflops. LLNL will use the computer to study cosmology and the behaviour of stellar binary pairs, laser-plasma interactions, and the behaviour and ageing of high explosives, according to IBM.

Two prototypes of Blue Gene, both at IBM's Thomas Watson Research Center, made the list in positions four and eight with respective rankings of 11.7Tflops and 8.7Tflops.

The ranking relies on computer owners or makers submitting details of their machines and is based on the results of a standard benchmark called Linpack. Machines are ranked by the maximum number of floating operations per second (flops) achieved during the test.

New at two

There were several other important changes in the top ten including a new machine at number two.

The Thunder system, based on 4,096 Intel Itanium 2 processors, at LLNL recorded a maximum performance of 20Tflops to gain second place and push Los Alamos National Laboratory's ASCI-Q machine into third place ahead of the first of the two Blue Gene prototypes.

On a geographical note, the new ranking also marks the first time a Chinese machine has made the top 10 and the return of Europe into the top of the chart.

The Dawning Information Industry-built 4000A computer at the Chinese Academy of Sciences' Shanghai Supercomputer Center achieved a ranking of 8.1Tflops to give it tenth place on the ranking while a new IBM eServer P690 system at the European Centre for Medium-Range Weather Forecasts was fast enough at 9Tflops to rank sixth.

In addition to the main ranking, the list also provides an easy way to keep a watch on trends in the supercomputing sector.

One such is the move towards the cluster architecture, in which a number of computers work together to form a more powerful machine. In the last ranking such machines, which include the Virginia Tech Apple Mac machine, totalled 208 and this has grown to 291 systems in the new list. That represents just under 60 per cent of all machines in the Top 500.

A look at the hardware shows Intel making big gains on its competitors: a total of 287 machines are based on Intel chips, up from 119 this time last year. IBM remains the top manufacturer accounting for 45 per cent of systems, ahead of Hewlett-Packard in second with 28 per cent.

The full Top 500 ranking can be found online. It is compiled by Hans Meuer of the University of Mannheim, Erich Strohmaier and Horst Simon of NERSC/Lawrence Berkeley National Laboratory, and Jack Dongarra of the University of Tennessee.