Search for prime numbers or torture your CPU with Prime95

Donate processor power or run system stress tests with this famous freeware.

You remember the story of Dr. Jekyll and Mr. Hyde? Well, that's sort of the story of Prime95, too. This mild-mannered mathematics software lets users participate in GIMPS, the Great Internet Mersenne Prime Search. This online project uses the distributed power of many networked PCs (like yours) to search for immense Mersenne prime numbers. Prime95 lets users donate processing power to the nonprofit research project. In the hot hands of overclockers, though, Prime95 becomes an instrument of torture, running stress tests that pinpoint weak links in your system. How you use Prime95 determines its behavior.

Prime95's setup wizard offers two distinct choices: Join GIMPS, or Just Stress Testing. We started with Just Stress Testing. A pop-up wizard labeled Run a Torture Test appeared. Tools like Prime95 stress your PC by running calculations at maximum power. The test gives several options, including tests that include very little or lots of RAM, or a blend of the two, and the results give a clear picture of your PC's performance, including processor speed and other data critical to overclocking.

We could specify the number of test threads to run as well as configure a Custom test. In the Advanced menu you can specify tests by exponent, time, and other factors; the Options menu accesses not only the Torture Test features but also a Benchmarking tool, CPU options such as when and how long the tests will run, and Preferences, including the option to play a sound if it finds a new Mersenne prime (the project has uncovered 13 since 1996). Like the GIMPS tool, some of the advanced features require a free PrimeNet account.

We ran a variety of benchmarking and stress tests on our system. Tests can be very brief or run continuously for true torture testing. Prime95 displays results in a split log view that can be customized in a variety of ways as well as copied, saved, and edited. Those interested in GIMPS should visit the project's site for more information. Whether you're the friendly, collaborative researcher or the (let's be frank) mad-scientist type, this top-quality software instrument has something to offer.

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