I have been watching the semi-annual 500 fastest super computer list for a while, and each time I look to see how many computers on the list are based on Microsoft Windows. This latest list (released this month) still doesn’t show much Windows love. Out of 500 super computers, there are 6 based on Windows. And two of those are partially based on Linux, so really only 4 of the 500 are purely Windows. That is really sad. But why is this happening?If you know me very well, you know that I am not a Microsoft fan. But this continual shunning of Windows in the World’s fastest computers puzzles me. I know the problem is not cost, because many of these super computers use uber-expensive operating systems from IBM and others. And I also know that the problem is not performance, because benchmarks I’ve seen show that the latest versions of Windows Server can compete with Linux/Unix in speed tests. So maybe the problem is scalability?Maybe when you tie thousands of Windows computers together, you get a performance hit. And maybe Linux/Unix can handle this kind of scale. But I even doubt this, because companies like eBay (not to mention Microsoft) have used Windows for years in their data centers to power some of the world’s most popular and demanding websites.So this leaves me with one conclusion. I think that Microsoft’s bad reputation is at play here. Everybody “knows” that Windows is a resource pig, right? At least, that is the common perception out there. I think the companies that are building these super computers are probably turning their noses up at Microsoft, purely based on reputation.