Personal computers are single-user devices for general purposes. While the performance of a modern personal computer can surpass that of the old supercomputers, they do not aim for maximum performance and the operating system is designed more towards software compatibility, usability, entertainment, office work, mobility, and the like. In 2021, roughly 80 % of personal computers use Microsoft’s Windows, while around 10 % run macOS, a proprietary operating system developed and run by Apple. The rest of the devices use Google’s Chrome OS or some version of Linux or Unix.
On the other hand, supercomputers are focused on performing intensive number-crunching mainly for scientific purposes and a large number of users. All supercomputers making the TOP500 have been using Linux for a couple of years.
Linux has many advantages over other operating systems when it comes to supercomputers. Unlike Windows and macOS, Linux is modular and built around a kernel containing the basic system and drivers. Because Linux is open-source, it is possible to customize the operating system for a special high-performance purpose. One can strip down all the unnecessary components and build a lightweight version with only the essential functionality and features. When running on a massively parallel scale (i.e., using tens or hundreds of thousands of CPU cores), even minuscule excess in the operating system can add up and limit the performance. Moreover, the license fees of proprietary operating systems are typically based on the number of CPUs, and in supercomputers, there are lots of them. As Linux is generally free, it allows considerable savings in software costs.