Marin Mersenne2^P-1
Username
Password
Forgot password?
Great Internet Mersenne Prime Search
GIMPS
Finding World Record Primes Since 1996
You are using the mirror

Free Mersenne Prime Search Software

Prime95 Version 28.5

Version 28.5 - See the latest WhatsNew.txt file for a list of changes.

This latest version of prime95 has been optimized for Intel's new AVX2 instruction set. Owners of Haswell CPUs (Core i3/i5/i7 4xxx) will see a significant performance increase.

Any modern personal computer with Windows, Mac OS X, Linux, or FreeBSD can participate. The How it Works page answers many questions you may have before downloading the software. You must also agree to the GIMPS free software license.

Unix and non-x86 users should check out Ernst Mayer's Mlucas page and the Glucas page for guidance as to which code is best for their platform.

Some software has been written for NVIDIA and AMD GPUs. Visit the Mersenne GPU Computing Forum for more information.

Setup Instructions for New Users

Joining GIMPS is usually as simple as downloading and running the program, answering a few questions, and the program does the rest.

There are cash awards for discovering a new Mersenne prime!

  1. If you have not done so, create your UserID. It's optional, but required to check your account details, computer status and performance statistics and to assign computers to your user ID.

  2. Download the appropriate free program for your OS and proceed to Step 3: Windows 64-bit, Windows 32-bit, Mac OS X Mavericks, Linux 64-bit, or one of the other special versions listed below.
    More details about these programs, plus and a few more versions for other operating systems, are given here:

    Operating System Version Released Size Download Notes
    Windows 8/​7/​Vista/​XP/​2008 64-bit28.52014-05-305.1MBp95v285.win64.zip
    Windows 8/​7/​Vista/​XP/​2008/​2003/​2000/​NT/​Me/​98/​95 32-bit28.52014-05-304.1MBp95v285.win32.zip
    Linux 64-bit28.52014-05-305.4MBp95v285.linux64.tar.gz
    Linux 32-bit28.52014-05-304.4MBp95v285.linux32.tar.gz
    Mac OS X28.52014-05-303.4MBp95v285.MacOSX.zipRequires Mac OS X Mavericks (10.9)
    Mac OS X command line version28.52014-05-303.5MBp95v285.MacOSX.noGUI.tar.gzNo GUI. Requires Mac OS X 10.7 or later and an Intel CPU.
    Mac OS X pre-Mavericks27.92012-12-125.1MBp95v279.MacOSX.zipRequires Mac OS X 10.3 to 10.8 and an Intel CPU.
    FreeBSD 64-bit28.52014-05-305.3MBp95v285.FreeBSD10-64.tar.gzRequires FreeBSD 10.0
    FreeBSD 64-bit27.92012-12-124.5MBp95v279.FreeBSD64.tar.gzRequires FreeBSD 8.0. May work on later versions.
    FreeBSD 32-bit26.62011-04-084.0MBmprime266-FreeBSD.tar.gzRequires FreeBSD 7.0. May work on later versions.
    Windows 8/​7/​Vista/​XP/​2008 64-bit Service28.52014-05-305.0MBp95v285.win64.service.zipThis is for administrators that want the extra security of running a traditional GUI-less service. You will still need to download the standard windows executable to configure the client. This program is for Windows Server experts only.
    Windows 8/​7/​Vista/​XP/​2008/​2003/​2000/​NT 32-bit Service28.52014-05-304.0MBp95v285.win32.service.zipThis is for administrators that want the extra security of running a traditional GUI-less service. You will still need to download the standard windows executable to configure the client. This program is for Windows Server experts only.
    Source code for Windows, Linux, FreeBSD, and Mac OS X28.52014-05-3042.7MBp95v285.source.zip
  3. Create a directory and decompress the file you just downloaded. Windows 8, 7, Vista, and XP have built-in unzip features. Other Windows users can choose from a variety of decompression programs. We use 7-zip. Linux and FreeBSD users should use the standard tar and gzip decompression utilities.

  4. Configure Primenet Start the program!
    Linux and FreeBSD users should run the program from the command line with a -m switch, i.e. ./mprime -m

    Enter your optional userID created on the website in Step 1, and optionally name your computer. We recommend Windows users select Options » Start at Bootup or Start at Logon.

    That's all you need to do! The program contacts a central server called PrimeNet to get some work to do. Usually the program and PrimeNet know the best work to assign, but it's up to you! You can administer your account and computers on your userID's account page. Once you complete a workunit you can track your standings on the competitive stats pages the server updates every hour (see Top Producers in the menu, left, for more stats). You can monitor each of your computers' progress, even remote-control the work assignments they request using your userID's CPUs page!
    Linux and FreeBSD versions can also be set up to run every time you restart your computer.
    Ask for help at the Mersenne Forum.

CPU Stress / Torture Testing

Prime95 has been a popular choice for stress / torture testing a CPU since it's introduction, especially with overclockers and system builders. Since the software makes heavy use of the processor's integer and floating point instructions, it feeds the processor a consistent and verifiable workload to test the stability of the CPU and the L1/L2/L3 processor cache. Additionally, it uses all of the cores of a multi-CPU / multi-core system to ensure a high-load stress test environment.

From the most recent "stress.txt" file included in the download:

Today's computers are not perfect. Even brand new systems from major manufacturers can have hidden flaws. If any of several key components such as CPU, memory, cooling, etc. are not up to spec, it can lead to incorrect calculations and/or unexplained system crashes.

Overclocking is the practice of increasing the speed of the CPU and/or memory to make a machine faster at little cost. Typically, overclocking involves pushing a machine past its limits and then backing off just a little bit.

For these reasons, both non-overclockers and overclockers need programs that test the stability of their computers. This is done by running programs that put a heavy load on the computer. Though not originally designed for this purpose, this program is one of a few programs that are excellent at stress testing a computer.

The Prime95 Wikipedia page has an excellent overview on using Prime95 to test your system and ensure it is working properly. The tips presented there should be helpful regarding how long to run the torture test and provide a solid guideline on how long to run the Prime95 stress test.

Performing a stress test is simple:

  1. Download the software and unzip the files to your desired location.
  2. Run the Prime95 executable and select "Just Stress Testing" when asked.
  3. The default options are sufficient to do a well balanced stress test on the system.

Upgrade Instructions for Existing Users

If you are upgrading from version 24, then get special instructions needed to first upgrade to the latest version.
  1. Download the appropriate program for your OS: Windows 64-bit, Windows 32-bit, Mac OS X Mavericks, Linux 64-bit, or one of the other ports listed below in the instructions for new users sections.

  2. Upgrade the software. Stop and exit your current version, then install the new version overwriting the previous version. You can upgrade even if you are in the middle of testing an exponent.

  3. Restart the program.

  4. Read whatsnew.txt.

Questions and Problems

Please consult the readme.txt file for possible answers. You can also search for an answer, or ask for help in the GIMPS forums. Otherwise, you will need to address your question to one of the two people who wrote the program. Networking and server problems should be sent to Scott Kurowski. Such problems include errors contacting the server, problems with assignments or userids, and errors on the server's statistics page. All other problems and questions should be sent to George Woltman, but please consult the forums first.

Disclaimers

See GIMPS Terms and Conditions. However, please do send bug reports and suggestions for improvements.

Software Source Code

If you use GIMPS source code to find Mersenne primes, you must agree to adhere to the GIMPS free software license agreement. Other than that restriction, you may use this code as you see fit.

The source code for the program is highly optimized Intel assembly language. There are many more-readable FFT algorithms available on the web and in textbooks. The program is also completely non-portable. If you are curious anyway, you can download all the source code (42.7MB). This file includes all the version 28.5 source code for Windows, Linux, FreeBSD, and Mac OS X. Last updated: 2014-05-30.

The GIMPS program is very loosely based on C code written by Richard Crandall. Luke Welsh has started a web page that points to Richard Crandall's program and other available source code that you can use to help search for Mersenne primes.

Other available freeware

At this time, Ernst Mayer's Mlucas program and Guillermo Ballester Valor's Glucas programs are the best choices for non-Intel architectures. Luke Welsh has a web page that points to available source code of mostly historical interest you can use to help search for Mersenne primes.