Great Internet Mersenne Prime Search and GIMPS for Windows PC



  -  8.4 MB  -  Freeware
  • Latest Version

    Prime95 30.19 Build 20 LATEST

  • Review by

    Michael Reynolds

  • Operating System

    Windows XP64 / Vista64 / Windows 7 64 / Windows 8 64 / Windows 10 64 / Windows 11

  • User Rating

    Click to vote
  • Author / Product

    Mersenne Research, Inc. / External Link

  • Filename

  • MD5 Checksum


Prime95 is a powerful and widely recognized piece of software that has been a staple in the world of PC enthusiasts and overclockers for many years. Developed by Mersenne Research, Inc., Prime95 is primarily known for its ability to stress test your computer's CPU, ensuring its stability and performance under heavy workloads.

Originally designed to search for Mersenne prime numbers, it has evolved into a versatile tool for evaluating the robustness of your CPU and system. In this comprehensive review, we will delve deep into the software, exploring its features, user interface, installation, usage, FAQs, alternatives, pricing, system requirements, and more!

Main Features

Torture Test Modes: It offers several torture test modes, including Small FFTs, Blend, and Large FFTs. These modes stress your CPU, RAM, and even the motherboard, helping you identify any hardware or stability issues.

Real-time Monitoring: The software provides real-time monitoring of CPU temperatures, core utilization, and other vital system statistics. This feature is especially useful for overclockers who need to keep a close eye on their hardware's performance.

Customizable Test Parameters: Users can customize the test parameters to tailor the stress test to their specific needs. Adjust factors like the number of threads, FFT size, and run-time to get precise results.

Error Checking: It detects and reports errors, allowing users to identify unstable overclocks or potential hardware problems quickly.

Benchmarking: In addition to stability testing, it can serve as a benchmarking tool, providing performance scores that can be compared to other systems.

User Interface

Prime95's user interface, while not flashy, is straightforward and functional. It adopts a no-nonsense design, making it easy for both beginners and experienced users to navigate. The main window provides access to the various test modes, settings, and real-time monitoring graphs. Despite its simplicity, the UI could benefit from a more modern design and improved aesthetics. However, the software's focus on functionality over form ensures that it gets the job done efficiently.

Installation and Setup

Installing the tool is a straightforward process. The software can be downloaded from the official website or trusted software repositories, like FileHorse. Once downloaded, simply run the installer, and you'll be guided through a few basic setup options, such as choosing a destination folder. There's no bloatware or unnecessary add-ons bundled with the installation, which is a refreshing change from many software packages.

How to Use
  • Download and install the app from the official website or FileHorse.
  • Launch the program and choose the "Just Stress Testing" option if prompted.
  • In the main window, select your desired torture test mode (e.g., Small FFTs, Blend, or Large FFTs).
  • Click the "OK" button to start the stress test.
  • Monitor your CPU temperature and system stability in real-time using the provided graphs and statistics.
  • To stop the test, click the "Test" menu and select "Stop."

What is the purpose of stress testing with Prime95?
Stress testing with the program helps identify hardware stability issues, especially when overclocking. It pushes your CPU, RAM, and motherboard to their limits to uncover any potential problems.

Can I customize the stress test parameters?
Yes, you can customize parameters like the number of threads, FFT size, and run-time to fine-tune the stress test to your specific requirements.

Does Prime95 work on all operating systems?
Prime95 is primarily designed for Windows but can also run on Linux and other platforms using compatibility layers like Wine.

Is Prime95 safe to use?
Prime95 is safe for stress testing your hardware, but it can generate a lot of heat. Ensure your system has proper cooling before running extended tests.

Does Prime95 support multi-threaded CPUs?
Yes, it takes full advantage of multi-threaded CPUs, making it an excellent choice for modern processors.


AIDA64: A comprehensive system information and benchmarking tool that includes CPU and GPU stress tests.

OCCT: Offers a variety of stress tests, including CPU, GPU, and power supply tests, with a user-friendly interface.

MemTest86: Primarily focused on memory testing, this tool helps identify RAM-related issues.

FurMark: Ideal for GPU stress testing, FurMark pushes your graphics card to its limits to assess stability and cooling performance.


The tool is FREE to download and use, making it an excellent choice for budget-conscious users who require robust stress testing capabilities without any additional cost.

System Requirements
  • Operating System: Windows 11, 10, 8 or 7 (32bit or 64bit)
  • CPU: 64-bit processor recommended
  • RAM: 1 GB or more
  • Disk Space: Minimal
  • Powerful stress testing capabilities for CPU, RAM, and motherboard.
  • Real-time monitoring of critical system statistics.
  • Customizable test parameters for advanced users.
  • Error detection and reporting for hardware stability.
  • Free to use with no hidden costs or bloatware.
  • Outdated user interface lacking modern design.
  • Limited appeal beyond overclockers and PC enthusiasts.
  • Generates significant heat during extended stress tests.

It remains a stalwart in the world of stress testing software, catering to overclockers, hardware enthusiasts, and users seeking to ensure the stability of their systems. While its user interface could benefit from a facelift, its extensive feature set, real-time monitoring, and error detection make it an essential tool for anyone pushing their hardware to the limits.

Best of all, it's free and offers exceptional value for those looking to stress test their PCs without breaking the bank. Whether you're an experienced overclocker or a novice user wanting to ensure your system's reliability, Prime95 has you covered.

Also Available: Prime95 for Mac

  • Prime95 30.19 Build 20 Screenshots

    The images below have been resized. Click on them to view the screenshots in full size.

    Prime95 30.19 Build 20 Screenshot 1
  • Prime95 30.19 Build 20 Screenshot 2
  • Prime95 30.19 Build 20 Screenshot 3
  • Prime95 30.19 Build 20 Screenshot 4

What's new in this version:

-  Huge improvements to stage 2 of ECM when lots of memory is available.
- Warning: prime.txt and local.txt files are automatically combined into one file. Consider backing up these files before installing.
-  Warning: upgrading in the middle of P-1 or ECM stage 2 may restart stage 2 from scratch