Prime95

Prime95 is the client software of GIMPS (Great Internet Mersenne Prime Search), a distributed computing project searching for Mersenne primes. Its torture test mode has long been used to stress test CPUs, in particular by overclockers and system builders.

Because the software makes heavy use of the processor’s integer and floating point instructions, it gives the processor a consistent and verifiable workload that tests the stability of the CPU and of the L1, L2 and L3 caches. It uses all the cores of a multi-core system, and errors in the computed results reveal hardware problems with the CPU, memory, cooling or power supply.

Prime95 is free software available for Windows, macOS, Linux and FreeBSD, under the GIMPS free software licence. Its source code is available.