Prime 95 for Windows

Aid in the search for Mersenne primes

Prime95 is a free application and the official client of GIMPS – the Great Internet Mersenne Prime Search. Designed to test numbers for primality using the Fermat primality test, Prime95 can also be used to stress-test your CPU in a similar fashion to software solutions like HeavyLoad and the Intel® Processor Diagnostic Tool.

For both functions, Prime95 works best when the computer running it is powered on more than it is off, as the program runs continuously in the background at the lowest possible priority.

Searching for prime numbers

Prim95’s main function is to search for undiscovered prime numbers using the Fermat primality test, as well as similar tests that help filter out unviable candidates. Prime95 requires a relatively modern computer that runs continuously in order to find new primes, as testing can take weeks or even months depending on the speed and age of the computer. Running in the background, it uses roughly 60MB of memory and 30MB of disk space per number.

Stress testing using Prime95

Prime95 is also a popular tool for overclockers and system builders who wish to stress test their CPU. Because the software requires heavy use of your computer’s processor with a consistent workload using all the cores of a multi-core system, Prime95 creates a high-load environment much greater than most computer programs, which is ideal when checking a particular configuration’s stability.

Hands-off multi-purpose software

Once Prime95 is installed, its use when searching for Mersenne primes is relatively hands-off and the software will simply run in the background at the lowest priority for as long as the computer is on. When stress testing your CPU, Prime95 only needs to be run for anywhere from an hour to a full day to create a high-load environment that’s sensitive to errors and capable of checking your CPU’s stability. For both functions, the stripped-down interface is easy to navigate.