More than 1,200 processors have been added to the system

The HPCx machine, based in Warrington, is now capable of operating at speeds up to 15.4 teraflops, or 15.4 trillion calculations every second.

The speed boost follows the addition of more than 1,200 processors to the four year-old, IBM-built number-cruncher.

The high-performance machine is used by scientists to simulate everything from ocean currents to biological cells.

The upgrade will allow scientists to run more complex models on the machine.

"What we've done throughout the computer's life is to keep the machine abreast of the way that computers are getting faster as a whole," said Professor Arthur Trew, director of the Edinburgh Parallel Computing Centre which heads the consortium that runs the system.

"The problem is that the demand for computational ability always outstrips the machine's ability to deliver it."

Although HPCx could achieve speeds of more than 15 teraflops, it typically ran at around 12 teraflops, Professor Trew said.

Speed trials

When HPCx first came into service in 2002 it was one of the top 10 fastest supercomputers in the world. Despite an upgrade in 2004, it has since slipped to 59th place in the Top 500 supercomputers list.

TOP FIVE SUPERCOMPUTERS Blue Gene/L, Lawrence Livermore National Laboratory, California. (131,072 processors) BGW Blue Gene, IBM Thomas J. Watson Research Center, New York (40,960 processors) ASC Purple, Department of Energy, USA (12,208 processors) Columbia, Nasa Ames Research Center, USA (10,160 processors) Tera-10, Commissariat a l'Energie Atomique (CEA), France (8,704 processors) Source: Top 500 Supercomputers

Although the upgrade will undoubtedly push HPCx up the rankings in the new list, published on 14 November 2007, the UK government and research community have already decided to replace it with a higher spec machine known as Hector.

Hector, or the High-End Computing Terascale Resource, will be owned by the Research Councils of the UK and will start operating in 2007. HPCx is planned to cease working in December 2008.

Hector could run at speeds of up to 100 teraflops, 100,000 times faster than an ordinary computer.

However, its normal operating speeds will be far less as supercomputers are only able to achieve their maximum speeds for short bursts of time.

Record-breakers

At the moment the most potent machine in the world is the IBM's Blue Gene/L at the Lawrence Livermore National Laboratory in California where it is used to ensure that the US nuclear weapons stockpile remains safe and reliable.

The most powerful computer in the world has 130,000 processors

The record breaking system, the only machine to have pushed through the 100 teraflop barrier, performs a staggering 280.6 trillion calculations per second. The computer has more than 130,000 processors and is thought to be capable of running at speeds in excess of 367 teraflops.

However, this will also soon be superseded when another IBM machine, codenamed Roadrunner, is built at the Los Alamos National Laboratory in the US.

The new machine will be able to achieve "petaflop speeds". One petaflop is the equivalent of 1,000 trillion calculations per second.

Running at peak speed, it will be able to crunch through 1.6 thousand trillion calculations per second.

In comparison, the fastest machines in the UK are owned and operated by the European Centre for Medium-Range Weather Forecasts (ECMWF) in Reading.

Their two identical computers were installed in August this year and are capable of carrying out just 34 trillion calculations every second.

The pair will run in parallel so that if there is a problem with one, the centre's forecasting ability can continue.