Super Pi

SuperPi is one of the most popular benchmarks with overclockers and tweakers. It has been used in world-record competitions since forever. It is a purely single-threaded CPU test that calculates Pi to a large number of digits—32 million for our testing. Released in 1995, it only supports x86 floating-point instructions and thus makes for a good test for single-threaded legacy application performance.

Y-Cruncher

Y-Cruncher is a highly optimized piece of software that can calculate Pi and other constants to a huge number of digits. It is fully multi-threaded, uses a modern code design and is optimized for all major processor architectures. This ability has made it a popular application that's used by the enthusiast community to determine and compare how powerful their overclocked systems are.