Concerns about high-performance computers being used for military purposes in China and Russia have spurred the United States to tighten export rules for workstations and servers. Early this month, the US Commerce Department issued rules that enable certain government departments to scrutinise the export of high-performance computers to the mainland and about 49 other countries. The rules apply to computers with speeds between 2,000 and 7,000 million theoretical operations per second (Mtops). But some industry observers say the rules may be overly restrictive, because the low end of the range would apply to some machines commonly sold to corporations, not just supercomputers. The rules implement a law passed last year tightening export procedures for high-powered computers destined for developing countries capable of building nuclear weapons. Those so-called Computer Tier 3 countries include China, Russia, Israel and India. The rules were passed following reports China and Russia had diverted high-performance computers for military use. A Sun Microsystems supercomputer was returned to the US last September after the government discovered it was diverted illegally from a civilian research facility to a military and scientific institute in Changsha, Hunan province. An industry source said there also had been investigations involving diverted equipment made by Silicon Graphics and its subsidiary, Cray Research. A US Consulate spokesman in Hong Kong said the rules applied not only to vendor sales, but also to resale of such computers to the mainland by companies or individuals in the SAR or Singapore. Industry sources said a 'grey market' channel in Hong Kong and, to a lesser extent, Singapore had enabled parties in those countries to resell powerful computers to mainland parties. In theory, Hong Kong and Singapore are allowed to import freely supercomputers and servers, but the US has called into question the purpose and usage of certain supercomputers exported to Hong Kong. Hong Kong University's purchase of an IBM Risc System 6000 supercomputer in 1996 had come under scrutiny by the US, the university's computer centre director Ng Nam said. The computer - which was the most powerful in Hong Kong at the time - needed an import licence and explanations detailing the kinds of applications to be run on it. 'I think they [the US Government] don't want it to be used in certain areas like nuclear reactors or biomedical warfare,' he said. HKU's computer is used in areas such as civil and structural engineering, robotic engineering, quantum and molecular studies of physics and chemistry problems and statistical studies. Under stipulations laid out by the US, access to it by nationals of certain countries can be denied. 'When they apply for an account code [that enables them to log into the computer], I have to check their passport,' Mr Ng said. Nationals from a specified list of countries are not permitted access, although an exception had been made for the mainlanders who were 'students and researchers of staff in Hong Kong'. Since 1995, the mainland has bought about 50 supercomputers from the US, purportedly for civilian use such as weather forecasting and earthquake prediction. Observers say the 2,000 Mtops speed is much slower than today's supercomputers. Sun Microsystems deputy managing director for China, Paul Li, said the threshold covered even low-end workstations that used more than three microprocessors and which were used commonly for general commercial applications. Mr Li said the law would affect 'a large number' of Sun's shipments to the mainland where its biggest clients were schools, banks and telecom companies. Sun did not keep track of the number of its units shipped to the mainland. According to analysts, Sun, Silicon Graphics and IBM have the biggest market share of servers and workstations in the mainland. Figures from the New Century Group show that more than 90,000 servers were sold to the mainland last year. The new rules were likely to slow, but not reduce, those sales, vendors said. US exporters must notify the Commerce Department's Bureau of Export Administration of any proposed exports to Tier 3 countries and identify the buyer. The bureau will then confer with the defence, energy or state departments, or the Arms Control and Disarmament Agency, which will have 10 days to object. Vendors also must provide the bureau with written reports on end-users within 30 days of the shipment. 'Since it's a new law, I can't speculate how far the law enforcement body will go,' Mr Li said.