The top500.org website evaluates high performance machines along various criteria and ranks them in order of performance. Based on the current Top500 list, dating from November 2007, 426 super computers use the Linux operating system, whereas only six run on Windows. Unix is second at six percent and is installed on 30 of the top 500 machines.

This is an improvement for both Linux and Windows over the June 2007 figures: just six months previously, the free operating system accounted for a “mere” 77.8 percent, with just two machines running on Windows. The list is updated every six months, and provides a mass of additional information such as the location of the computers, applications, architectures and processors. Users can click to compile more statistics. For example, you can discover that more than half the machines are located in the USA: the largest (known) user group is the finance sector, which accounts for 14.4 percent, and Skalar is the main processor architecture with 99.2 percent, frequently on Intel EM64T at 64 percent. IBM sold 46.2 percent of the machines, followed by HP at 33.2 percent.

A team of scientists led by Professor Hans Meuer from the University of Mannheim introduced the list of the top 500 super computers back in 1993 in cooperation with vendors, generally available statistics and user surveys. The list puts the machines in order of performance, as ascertained by the LINPACK benchmark. This high performance computer benchmark asks the computers to calculate a system of linear equations. According to the authors this test is widespread in the HPC category and available for more or less any system.

netlib.org, a website for mathematical software, databases and documents provides detailed information on the benchmark test and the latest LINPACK Report.