There are many CPU and GPU stress tests available online that you can download on your computer and run for checking how your computer hardware fares during extreme load conditions. Some of these tests use mathematical calculations while other depend on the graphics related functions. One of the common tests done by these programs is the calculation of the precise value of PI to a very very large number of decimal places. This calculation is done in many iterations and after each iteration, the program gets a much more accurate value of PI.
Hyper PI is one of these stress test programs that was written to both find the value of PI to 32-million number of decimal places and to check how your brand new computer performs in this simple test. Hyper PI is actually based on another program called Super PI which was written in 1995 by the students of Tokyo University in Japan. Back then there were no multi-core processors and as such Super PI was designed to use single thread and single core. In those days it took many hours for it to calculate the value of Pi even to 1 million decimal places.
Now with Hyper PI, you can use the original approach of Super PI but using multiple cores and threads of modern computers. I tested Hyper PI on Intel Core i3 quad-core processor and it took less than half a minute to calculate the value of PI up to 1 million decimal places. One can only wonder how fast it would be on the latest Intel Core i9 processors.
In the Hyper PI user interface you can choose the number of digits of PI to be calculated, the CPU process priority, number of cores to be used, and whether to disable some CPU intensive features such as Audio, Themes or Aero. After this, you can click on Start and wait for it to finish.
In my case, it really made the processor work hard for a few seconds as I could hear the laptop fan running at top speed. As soon as the calculations were completed, the fan also stopped.
You can download Hyper PI from http://virgilioborges.com.br/hyperpi/.