Prime95 Tutorials & Guides
Prime95 is a freeware program by George Woltman, built for GIMPS, the search for Mersenne prime numbers. Its Torture Test mode compares nonstop calculations against known correct results, which makes it one of the most demanding ways to check whether a CPU, its cooling and your RAM are truly stable. These tutorials walk through the test one topic at a time, using only the program’s own documentation as the source.
Key facts before you start
Current version: Prime95 30.19 build 20. Cost: free (freeware, not open source). Windows is the only platform with a graphical interface; Linux and macOS use the command-line version called mprime. The official stress.txt guide recommends a 6 to 24 hour Torture Test for a thorough stability check.
All tutorials
How to Use Prime95
A complete beginner walkthrough: downloading, extracting, starting the Torture Test and stopping it safely.
Small vs Large vs Blend FFTs
What each Torture Test preset actually stresses, and which one to pick for CPU heat, cache or memory testing.
How Long to Run Prime95
The official stress.txt guidance of 6 to 24 hours, short 10 to 15 minute checks while overclocking, and what no run length can promise.
How to Disable AVX in Prime95
Reduce AVX-driven heat by adding CpuSupportsAVX settings to prime.txt, and understand what that changes about the test.
Prime95 on Linux: The mprime Guide
Linux has no GUI version. Run the command-line mprime, open its menu with ./mprime -m and configure workers from the terminal.
Prime95 on Mac: The mprime Guide
macOS also uses command-line mprime. The current build is Intel x86_64 only, so Apple Silicon Macs run it through Rosetta 2.
Prime95 Portable Use
Prime95 runs from an extracted folder with no installer and no administrator rights. How portable use works and what to keep writable.
Prime95 Benchmark Mode
What the built-in benchmark measures, how to run it, and how to read the throughput results it reports.
Prime95 Worker and Thread Setup
How workers map to your CPU cores and threads, and how to configure them for a balanced stress test.
Reading Prime95 Results
How to interpret results.txt, worker output and error lines so you know whether a run actually passed.
Where to go next
New here? Start on the download page for the current release and its verified SHA-256 hashes. Quick questions are answered in the Prime95 FAQ, and if a run stops early, the troubleshooting hub explains what each error means.