IBM remains owner of the fastest computer in the world, the latest Top500 list of supercomputers reveals.

In fact, Big Blue snagged six of the top 10 spots, including the coveted number one and two spots while widening the performance gap between it and its competitors. The list will be announced soon at the International Supercomputing Conference in Heidelberg, Germany.

For the second time, IBM's BlueGene/L System at the US Department of Energy's Lawrence Livermore National Laboratories in California, was the fastest supercomputer in the world. BlueGene/L has also doubled its performance over the past six months to reach a new Linpack benchmark performance of 136.8 teraflops or one trillion floating point operations per second, nearly double the 70.72 teraflops recorded in November - the last time the list was compiled.

According to Dave Turek, IBM vice president for Deep Computing, the company expects the system to again double in size over the summer up to between 270 and 280 teraflops.

In the number two position was the Watson Blue Gene (WBG) system, which IBM installed at its Thomas J. Watson Research Center in Yorktown, New York, last week. WBG had a benchmarked performance of 91.2 teraflops and is being used by IBM to conduct scientific and business research.

While BlueGene's speed and performance have been important to its rapid adoption, the supercomputer's small form factor has also proved attractive to customers, according to Stacey Quandt, IT analyst at Quandt Analytics. She also emphasized the continuing adoption of Linux - with eight of the top 10 supercomputers running on the open-source OS.

Silicon Graphics' Columbia system at NASA came third with 51.87 teraflops. In fourth position was the previous number one fastest supercomputer prior to BlueGene/L - NEC's Earth Simulator in Yokohama, Japan, with a Linpack benchmark performance of 35.86 teraflops.

The fastest supercomputer in Europe nabbed the number five spot, an IBM machine, the MareNostrum cluster at the Barcelona Supercomputer Center in Spain, with a performance of 27.91 teraflops. Just behind it was another BlueGene owned by Astron and run at the University of Groningen in the Netherlands with a performance of 27.45 teraflops. "The biggest surprise for us is the dominance of BlueGene at the very top end of the list," said IBM's Turek. He also pointed to MareNostrum's success as indicative of "a shift in the center of gravity outwards" through Europe away from the traditional supercomputer leaders Germany, France and the U.K.

There was a substantial shake-up in the Top500 list with half of the top ten systems from November being displaced by newly installed systems and the last 201 systems from the November list being too small to be listed anymore.

Intel's processors powered 333 systems on the list. The company's Pentium 4 was used in 175 supercomputers and its Itanium 2 was in 79 of the systems. IBM's Power chips were used in 77 of the machines, while Intel's Xeon Extended Memory 64 Technology (EM64T) was used in 76 of the computers. HP's PA Risc processors were used in 36 systems and AMD's Opteron in 25 systems.

In global terms, the US is still by far away and the market leader with 294 of the top 500 supercomputers up from 274 in November. Japan had 23 systems, while systems elsewhere in Asia accounted for 58 supercomputers. In Europe, which had 114 of the fastest supercomputers, Germany now has the most systems, 40 compared to UK's 32. Six months ago the situation was reversed with the UK as number one in Europe with 42 systems compared to Germany's 35 systems.