The Big Mac supercomputer – which combines 1,100 dual-2GHz Power Mac G5s – is officially ranked the world's third fastest computer.

The Top 500 ranking ranks machines on the maximum number of floating operations per second (flops) achieved during the test.

Virginia Polytechnic Institute and State University's Big Mac super computer came third, with a 10.3 teraflops. Each of the clsuter's G5s is connected using Infiniband interconnect technology and Gigabit Ethernet switches.

The top two positions are unchanged, with the NEC-built Earth Simulator at the Japan Marine Science and Technology Center ranked number one, with 35.9T flops (teraflops), and the Hewlett-Packard-built ASCI-Q machine at Los Alamos National Laboratory ranked number two, at 13.9T flops.

The Big Mac cluster also offers value: it cost just $5.2 million, while the top two clusters cost in excess of $100 million to set-up.

Linux is also making a good showing for itself. In the six months since the last ranking, an additional three Linux clusters win top-ten places.

A cluster of Dell PowerEdge 1750 servers with a total of 2,500 Intel Xeon 3.06GHz processors, and running Red Hat Linux, was fourth. The machine, which is at the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign, achieved a maximum performance of 9.8T flops.

Pacific Northwest National Laboratory's MPP2 computer was the fifth-ranked machine with a maximum performance of 8.6T flops. The computer consists of Hewlett-Packard Integrity RX2600 computers, and includes a total of 1,936 of the 1.5GHz version of Intel's Itanium 2 chip. It runs Red Hat Linux.

Linux boost The final new entry, at sixth, is the Lightning cluster at Los Alamos National Laboratory (LANL). The computer is the fastest system in the ranking based on Advanced Micro Devices' Opteron processor and also the first machine to enter the top 10 based on the chip. It includes 2,816 of the processors and achieved a maximum performance of 8.1T flops, according to the ranking. The computer was supplied by Linux Networx.

With these new machines and others, there are now 208 computer clusters in the Top 500 – up from 149 in the previous study six months earlier, said the list compilers.

The latest list also marks the emergence of China and Chinese computer makers as growing supercomputing powers.

Deepcomp 6800, a machine based on 1,024 of Intel's Itanium 2 processors running at 1.3GHz, built by the country's Legend Group Ltd., is ranked 14th, at 4.1T flops. In terms of the maximum performance of a single machine, it also puts China ahead of all other nations except the US and Japan. The computer is installed at the Chinese Academy of Science (CAS), according to the ranking.

The previous most powerful computer in China, Deepcomp 1800, also installed at CAS, ranked 82 in the new list and has achieved a maximum performance of 1.3T flops.