Introduction

Japan with half of the population and one twenty-fifth the geographical size of the United States, has over the last few decades become an economic giant. In correspondence to its economic ambition the country has established itself both as a large producer and consumer of supercomputing systems. As a result, the country finds itself well represented in the TOP500 list. Not only can the Japanese point to the single most powerful computer system on the list (for the second year in a row), the so-called Numerical Wind Tunnel installed by the National Aerospace Lab, but also to an accumulated Rmax per inhabitant that for the first time exceeds that of the US and is over four times that of Europe. Although it is true that Japan has fewer installed systems than Europe, this simply means that the Japanese systems are much more powerful on average than the European ones.

In order to review today's TOP500 installations it is extremely relevant to look at the development of the Japanese computing industry in a historical perspective. About 30 years ago, Japan was entirely dependent on American computing equipment (mainly made by IBM). To reduce their dependency on foreign systems, the Japanese employed a scheme of strong governmental support for reproducing other companies' computer designs and began to build up their own computer industry. For about two decades they were largely content to produce mainframes that imitated the IBM/370 systems, selling them in the local market with a Japanese MVS (Multiple Virtual Systems) look-alike operating system, or as plug-compatible machines abroad.

In recent years we have seen several changes in this scenario:

• First of all the Japanese companies now dominate the domestic market by providing an impressive 80% of all computer equipment. Japanese hardware technology is now state-of-the-art.
• All the large Japanese manufacturers have expanded beyond mainframes into supercomputers and can today claim to have the fastest supercomputers on the market.