OCCT is described as 'all-in-one stability check & stress test tool. OCCT is great at generating heavy loads on your components ( CPU, GPU, Memory, GPU Memory & Power supply ), and aims at detecting hardware errors or stability issues faster than anything else' and is a Benchmark tool in the os & utilities category. There are more than 10 alternatives to OCCT for a variety of platforms, including Windows, Linux, Android, Mac and iPhone. The best alternative is AIDA64. It's not free, so if you're looking for a free alternative, you could try HeavyLoad or Prime95. Other great apps like OCCT are GtkStressTesting, 3C Toolbox, Linpack Xtreme and LinX.
AIDA64 is a system information, diagnostics, and auditing application developed by FinalWire Ltd., that runs on Windows, Android, iOS, Windows Phone and Tizen operating systems. It displays detailed information on the components of a computer.
Linpack is a benchmark and the most aggressive stress testing software available today. Best used to test stability of overclocked PCs. Linpack tends to crash unstable PCs in a shorter period of time compared to other stress testing applications.
Super PI is a single threaded benchmark that calculates pi to a specific number of digits. It uses the Gauss-Legendre algorithm and is a Windows port of a program used by Yasumasa Kanada in 1995 to compute pi to 232 digits.