Marin Mersenne 2^P-1
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Great Internet Mersenne Prime Search
Finding World Record Primes Since 1996
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Free Mersenne Prime Search Software

Prime95 Version 30.3 build 6

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.
Latest version: 30.3 build 6 - see the latest WhatsNew.txt file for a full list of changes. Recent changes include:

Older version history

Highlights of version 29.8 include

  • AVX-512 support
  • Modified torture test dialog box with new options and better understanding of the L1/L2/L3 cache hierarchy
  • More robust implementation of Gerbicz error checking in PRP tests. This replaces LL testing as the default work type

Highlights of version 29.4 include

  • GIMPS has a new sub-project -- finding (probable) prime Mersenne cofactors
  • Like LL tests, PRP tests now support shift counts to aid in running double-checks
  • PRP tests now support a type of low overhead error checking that almost guarantees correct results even on flaky hardware
  • Because PRP tests are highly reliable, we now offer the option to do PRP tests instead of Lucas-Lehmer primality tests
  • For non-base-2 PRP tests, there is a new option to run each iteration twice and rollback if a mismatch occurs

Highlights of version 29.3 include

  • Enhanced error checking for LL tests
  • Faster step 1 GCD for ECM and P-1 factoring

Highlights of version 29.2 include

  • New benchmarking routines to determine the optimal FFT code
  • Changes to default CPU cores assigned to each worker to optimize total throughput per system
  • Optimized FFT sizes for AMD Ryzen
  • The new code will now do multithreaded trial factoring
  • Faster factoring code using FMA if available
  • Improvements to the hyperthread core detection

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 (see below for GPU software) and proceed to Step 3:

    Operating SystemVersionReleasedSizeDownloadNotes / Checksums
    MD5:    7ff8691ab8671b19d1ddf730c5df85d0
    SHA1:   9e10f6cd8f6db8584aa94259d21a683d3ba64c47
    SHA256: 533eda6a585cd047b3d41fba85bd52798ad6f4d8572b25a5f01ffdaae11509da
    MD5:    84b04ad9ae070d316a3e0bdc31d279be
    SHA1:   e4840ec69312a9f241e4b1defd725e06ec4cda52
    SHA256: ca712ceb3c3a9642acb6c6a45b9f3164a1f0aaec72dab4e47083ab07916b03f4
    Linux: 64-bit30.3b62020-09-116.7MBp95v303b6.linux64.tar.gz
    MD5:    a82efb2ccf4dc7aae818f0d39389e2ae
    SHA1:   65abdcec842241862b9bb2a91876f710fb8e57b1
    SHA256: ee54b56062feb05c9f80963a4e3ae8555d0e59ca60ddbcba65ce05225c9b9a79
    Linux: 32-bit30.3b62020-09-115.4MBp95v303b6.linux32.tar.gz
    MD5:    de6c04a80f13eb127b7fcba3cf5dd4b5
    SHA1:   fe44309760b8517f8ba68e38c515de9ff0d0cfa3
    SHA256: 403cbe638f047557acb9f31e3b54e4946c587ec4e6357d15711bf34cd210ff75
    Mac OS X29.8b72020-03-195.0MBp95v298b7.MacOSX.tar.gz
    Requires Mac OS X 10.9 (Mavericks) or later
    MD5:    5a110a0a5210fd10d7b8da0ce9ff43cf
    SHA1:   5a93d5f45dadd09b60520176f9abaead7c22d356
    SHA256: 3a0e228ea35bd96824163c7f5ab8e21502a33ae647752de3e5aab0f88fc7c52e
    Mac OS X
    command line version
    No GUI. Requires Mac OS X 10.7 or later and an Intel CPU.
    MD5:    9b6920d933d3c70eadd5a0942088881c
    SHA1:   7a20a100697c2c545db2f45c7973378d46875ccb
    SHA256: d0b4e447f67249dd5483dc1afc883e535c69632787eb70e9f42e9c15fed04a26
    FreeBSD 11+: 64-bit30.3b62020-09-117.1MBp95v303b6.FreeBSD11-64.tar.gz
    Requires FreeBSD 11.0
    MD5:    ae954c3f06363921e3f5e85c5aef7579
    SHA1:   20ec9babbffdbb9963c90d7a77d2a0d55c3dbc31
    SHA256: 4a6d6d7f0649ea958b0094e9644908c131b4aaa2a15bd69abf15ae3a661d8472
    Windows Service:
    This 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.
    MD5:    99196a3651760cc9cf3a2edb2da4ad5f
    SHA1:   f89c680cc61838bb0fa3f1a8639cff75674523d1
    SHA256: 6b79f82e20b630cf0596cbe18a77d2d86dbd62c3fb34d7bbb409c0ee1ef2d84d
    Windows Service:
    This 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.
    MD5:    c1fc1b8de42dd336700878582fa46b86
    SHA1:   9bee58679aede9cafb4eef469054ba9163a71070
    SHA256: 98959515c523c1e38bf59a86669f943dd24e31e16da81245481eb2e5e15e24df
    for Windows, Linux, FreeBSD, and Mac OS X
    MD5:    f894ce4da283e779668b27122022dfe7
    SHA1:   9d98a7de961d727a621aa3697fb81da6e2397314
    SHA256: bb5562a37d5ab15efc4cbf80e20e240410196efef2ce82df3b89768551bda270

    GPU Software

    If you have a recent discrete videocard powered by an AMD or NVIDIA GPU, it's potentially more powerful than your CPU at prime-testing (or factoring) Mersenne numbers.
    Visit the Mersenne GPU Computing Forum for more information.

    Some Mersenne-related software has been written for NVIDIA and AMD GPUs, including:

    Legacy Operating Systems
    Mac OS X
    Requires Mac OS X 10.3 to 10.8 and an Intel CPU.
    MD5:    0390ae2ff3d4a7082927482d82e62f59
    SHA1:   5f08298fb4aff5dbbab3d072519cd80ecce576c1
    SHA256: c44e3bdae50d3360ec58a0efff47ccfdff5bdc5d31f669e2761da4737d5560d8
    FreeBSD 10: 64-bit28.72015-08-105.3MBp95v287.FreeBSD10-64.tar.gz
    Requires FreeBSD 10.0
    MD5:    5dd21b471946fdcb4858a9fa50fe718b
    SHA1:   5143e7e355f8fdbce5b3629cc9cd8d4e9bd04592
    SHA256: 0a04bb01524e7c10edce501f57e902b3ce9f82cda0e39aaae8bfaa1af95ab416
    FreeBSD 8: 64-bit27.92012-12-124.5MBp95v279.FreeBSD64.tar.gz
    Requires FreeBSD 8.0. May work on later versions.
    MD5:    c6b1c84a79bb1b2e8366a81ddea0087c
    SHA1:   0f2972edb728a017b3bfe7da5cb7fddad7ed785c
    SHA256: 5ab9feddeb53fca9d9684119fae7ac271de3d85a4dd3c3f1fd26ab97ff71c05a
    FreeBSD 7: 32-bit26.62011-04-084.0MBmprime266-FreeBSD.tar.gz
    Requires FreeBSD 7.0. May work on later versions.
    MD5:    d7e78a458b0c7ebbd6db57ff08835739
    SHA1:   b283278dea4887494ebb7357992981ece8df3e08
    SHA256: d4c2c044cfa45311dd7f2c41574f59a0519c989fd6e0ca723505dea12b2ff1fd
    Windows XP:
    MD5:    4f7d1cc7904d5d9ccb26c8c00b6470a9
    SHA1:   54dd8f9b4692d7a878626ac993562b83cb5587fb
    SHA256: cdd32b4c358869d3f588ae430bc67d9e88a5a69506002f864adac3c477c9202a
    non-x86 OS

    Unix and non-x86 users should check out Ernst Mayer's Mlucas page .

  3. Create a directory and decompress the file you just downloaded. Windows 10, 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 its 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

  1. Download the appropriate program for your OS

  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 GIMPS admin. 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.


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

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 is the best choice 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.