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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 30.19 build 15

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: 30.19 build 15 - see the latest WhatsNew.txt file for a full list of changes. Recent changes include:

Older version history

Highlights of version 30.8 include

  • Huge improvements to stage 2 of P-1 when lots of memory is available.
  • Warning: upgrading in the middle of P-1 stage 2 will restart P-1 stage 2 from scratch

Highlights of version 30.7 include

  • Intel Alder Lake support. Improvements to stage 2 of P-1, ECM. Added P+1 factoring.
  • Warning: upgrading in the middle of P-1 stage 2 will restart P-1 stage 2 from scratch

Highlights of version 30.3 include

  • PRP with proofs. Eliminates the need for lengthy double-checking!!!
  • Resource Limits dialog box to control Prime95's resource usage. See the readme.txt file for setting these options

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:    5cf4ebd9f7a933cb133df50c5ec6b266
    SHA1:   6155a9d0fc2185551f225bf2c9fce33793094a6b
    SHA256: 47e39764ceca39e493e51e04ce1973bc9481efe7022a697d77e012772b9ca37d
    MD5:    177f316e65f059d98d006978d01af7f8
    SHA1:   259efce89cd1572d7a3b3fca04b59e107fe26cf4
    SHA256: b13a78ff6015df46ef6ba6ed7470e7275e0e095d06d4c019e70d571627235eb2
    Linux: 64-bit30.19b152024-05-015.6MBp95v3019b15.linux64.tar.gz
    MD5:    e41d38512ec013ae458e043e7e539d93
    SHA1:   7ed21c0b7f3336f4a5bd381fc9bb5172b2ecad77
    SHA256: 758e43f56683b5ec0401cd75f8e761da59341ccb7f343d5a9e3e12f44f9bda42
    Linux: 32-bit30.19b152024-05-014.5MBp95v3019b15.linux32.tar.gz
    MD5:    d64a93eb12c509ac4e1207b00ef7c897
    SHA1:   6126f5ddc3c6ca922119ae8bd94e5b0d68520442
    SHA256: 3ec9e4aed4204f2f3ea99e082dcc2a022d82dfdef3fba1b9f71a112d652d2711
    Mac OS X30.19b152024-05-014.3MBp95v3019b15.MacOSX.tar.gz
    Command line version, requires Intel CPU, Mac OS X 10.9 (Mavericks) or later
    MD5:    47726543c05a97f47a3fb4da491ae7ac
    SHA1:   4b145deb7409de8cd1f5523571dba8e22685c875
    SHA256: ed28d371c8bf6f5c22b2cd90a78d13fea4036070e63d7fd88a6bc643c858daa4
    FreeBSD 12: 64-bit30.19b152024-05-015.9MBp95v3019b15.FreeBSD12-64.tar.gz
    Requires FreeBSD 12.0
    MD5:    cc6075a192bf4c205c8544dc463ab070
    SHA1:   a8c90ded3c368ffd1c1a313e84fed03c06f7173f
    SHA256: dd87195645eadc69a1742290c1d818ab92e5bb07a83ab2aaef3abd4e4fd6b572
    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:    5b6c69c7ecb5740f48b2a108b4fd6d83
    SHA1:   fa301f8b0b7151677df1836cdab1e087f40d2f41
    SHA256: 2d3b44ea1b3c73d7b8f5f96dcaca45d0c7f5abae96e93f121b994f34e38424a2
    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:    d0762a63220667ad624e584566b32e09
    SHA1:   2679c570f3db0200a3f864f686cfbbb2e5f8e2d9
    SHA256: 6edd775dfbac35ff7fb790db4243e6f6194145935c5144c651ecb415ef8d870b
    for Windows, Linux, FreeBSD, and Mac OS X
    MD5:    8df2429e0df89b9153f098e0ad8d2ce2
    SHA1:   5bc15a817ccdbd81be0bc281488ee5f76feea6aa
    SHA256: 607ec82effcd6ffb39e3a6aafd2f04d543cf5c5cbf8cb1a8054f6ace273861b2

    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, GUI version29.8b72020-03-195.0MBp95v298b7.MacOSX.tar.gz
    Requires Intel CPU, Mac OS X 10.9 (Mavericks) or later
    MD5:    5a110a0a5210fd10d7b8da0ce9ff43cf
    SHA1:   5a93d5f45dadd09b60520176f9abaead7c22d356
    SHA256: 3a0e228ea35bd96824163c7f5ab8e21502a33ae647752de3e5aab0f88fc7c52e
    Mac OS X
    Requires Mac OS X 10.3 to 10.8 and an Intel CPU.
    MD5:    0390ae2ff3d4a7082927482d82e62f59
    SHA1:   5f08298fb4aff5dbbab3d072519cd80ecce576c1
    SHA256: c44e3bdae50d3360ec58a0efff47ccfdff5bdc5d31f669e2761da4737d5560d8
    FreeBSD 11+: 64-bit30.7b92021-11-157.1MBp95v307b9.FreeBSD11-64.tar.gz
    Requires FreeBSD 11.0
    MD5:    a88718f5d985c3a0e0f76323969ffcaf
    SHA1:   767e890fb914e5a81b0ee6c0df9b4624408caf4a
    SHA256: 750a36bce52d33db7c6765ea454d12a25aea0b967b99642d3847cb87c7e844a5
    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 download all the source code (38.8MB). This file includes all the version 30.19b19 source code for Windows, Linux, FreeBSD, and Mac OS X. Last updated: 2024-05-15.

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.