IBM's Blue Gene/L supercomputer has kept its position as the most powerful number cruncher in the world. Its hold on the top slot was revealed in the latest list of the Top 500 supercomputers on Earth.
Blue Gene/L was top of the biannually produced list because in June 2005 it set a new world record performance of 280.6 trillion calculations per second.
It could head supercomputer rankings for a while as it has still not reached its maximum possible performance.
The machines in the top two slots of the Top 500 are unchanged from the last list produced in June 2005 and both are IBM Blue Gene machines.
Blue Gene/L is installed at the Lawrence Livermore National Laboratory in California and the other Blue Gene machine is at IBM's Thomas J Watson research lab in New York state.
The Blue Gene/L machine has doubled in size since the last list was compiled and now harnesses the computational power of more than 130,000 processors.
Although it set a record by carrying out more than 280.6 trillion calculations per second (teraflops), it has a theoretical maximum performance in excess of 367 teraflops. No other supercomputer has broken the 100 teraflops barrier.
This could mean that it breaks the record for the machine that stays longest in the number one slot on the Top 500 list. NEC's Earth Simulator machine, with a peak performance of 35.86 teraflops, topped five consecutive lists. Now that machine has slipped to the number seven position.
The increase in computational power of the Blue Gene/L shows the rapid pace of supercomputer development.
In the latest Top 500, four of the top 10 systems from the previous list were bumped out by more powerful machines.
New in at the number three position is the Asci Purple system that is also based at the Lawrence Livermore lab.
The entry level for the top 10 machines is 20.53 teraflops, even though a year ago it was just under 10 teraflops. To make it into the Top 500, supercomputers must be capable of at least 1.64 teraflops performance.