Hong Kong has risen in the ranks of owners of the world's fastest supercomputers by doubling the number of its high-performance computing sites over the past six months. Recent installations at Hutchison Telecom and Hong Kong Baptist University have joined systems at the University of Hong Kong and an undisclosed financial institution on the latest list of the top 500 supercomputers, announced last month. With four supercomputers making the list, Hong Kong has leapfrogged economic rivals Singapore and Taiwan, each of which have a pair of supercomputers, in the latest rankings. Hong Kong had two supercomputers in the top-500 list in November. Yet Hong Kong remains behind other large Asia-Pacific markets. China and Australia each have five supercomputers, while South Korea has 12. Japan led the region, with 40 systems making it into the 21st list of the world's top 500 supercomputers. The Earth Simulator supercomputer, built by NEC and installed last year at the Earth Simulator Center in Yokohama, retained the No 1 position with its ability to do 35.86 'teraflops', or trillions of calculations a second. The top-500 list is released twice a year by researchers at the Universities of Tennessee in the United States and Mannheim in Germany. The list ranks supercomputers based on the Linpack Benchmark, a yardstick of performance that measures processor speed and scalability. The world's toughest computing challenges are tackled, and often solved, on bulky supercomputers and so-called clusters - networked personal computers, servers or workstations used as a single system to solve a complex problem. These machines have been used over the years in diverse areas such as meteorological modelling, human genome mapping and nuclear blast simulation. Legend Group's 'Deepcomp 1800' system in Beijing took the top position among supercomputers from Greater China, ranking No 52 on the list. The fastest computer yet developed in the mainland, it can perform a trillion calculations a second. It was deployed last September at the Academy of Mathematics and System Sciences, part of the Chinese Academy of Sciences. The main shift in the high-performance computing market involves a growing trend to use clusters of commercial, off-the-shelf personal computers based on Intel processors. 'Cluster computing makes it possible for Hong Kong commerce and industry to become more productive by having many PCs work on a problem at the same time,' said Fred Hickernell, a professor in Hong Kong Baptist University's mathematics department and the director of the university's High-Performance Cluster Computer Centre (HPCCC). The HPCCC system, based on Dell PowerEdge computers running 128 2.8-gigahertz Pentium 4 Xeon processors, was ranked No 300 on the list of supercomputers. This cluster is the fastest academic supercomputer in Hong Kong, besting a 64-processor IBM SP supercomputer deployed since 2001 at the Chinese University of Hong Kong. Listed at No 340 is the Gideon cluster, developed by the systems research group at the University of Hong Kong. This set-up consists of a group of student-built PCs which collectively run 300 2GHz Pentium 4 chips, connected by a 312-port networking switch. The top-ranked supercomputer from Hong Kong, at No 235, is the unnamed financial institution's IBM SP supercomputer, running 424 375-megahertz Power3 processors. Hutchison Telecom's supercomputer, an HP Superdome HyperPlex running 128 875MHz processors, was listed at No 435 in the top 500. HP held on to its lead as the maker of the most supercomputers, with a total of 159 systems. Closest competitor IBM had 158 machines on the list. The number of clusters in the top 500 grew to reach 149 systems from just a handful about three years ago.