Prime95 — Download
An extensive CPU stress test diagnostic which searches for prime numbers, execute Lucas-Lehmer primality test.
Prime95 is a bench-marking application used to test the power of your CPU, or processor.
The utility of this program is great, putting your CPU to the test by finding prime numbers, numbers which are only divisible by 1 and themselves. This is a great idea for pushing a CPU to its limits by harnessing its processing power.
By using Prime95 on a system, you’ll find an excellent tool to test the performance level and stability of a CPU and by extension, a PC.
As on of the top choices for overclocking enthusiasts and system tweakers, Prime95 is a good companion to heat up your PC and testing its limits by running it under experimental conditions, such as upping the clock rate and voltage. It can be ultimately useful to test whether cooling fans or water-heating are sufficient for high-powered gaming setups.
The Torture Test feature of Prime95 is the best way to put your processor and memory to the test. This mode will run a succession of tests: Small TTS, In-place large FFTs and Blend. The latter being the most intensive of the three tests. Passing these tests means the PC is ready to go, but keep in mind that it could take an entire day for Prime95 to do its magic.
As with any type of PC stress test, you should keep an eye on the target system and the temperatures.
As a freeware tool, Prime95 competes with other applications like IntelBurnTest or CPU Free Benchmark but has come to be the gold standard. An online community of overclockers and other enthusiasts exist where users of Prime95 can share their test results with the wider world.
All in all, Prime95 serves as the gold standard in system stress testing and bench-marking, making it an essential companion to anybody wishing to test the stability of their system setup.
Features of Prime95
- CPU stress testing: Prime95 is known for its ability to stress test a computer’s central processing unit (CPU) to ensure it’s functioning properly and can handle demanding tasks.
- Compatibility with overclocking: Works with overclocking, making it a useful tool for enthusiasts who want to push their hardware to its limits.
- Continuous testing: Run the stress test continuously, allowing users to test the stability of their system over a long period of time.
- Customizable test options: Customize the stress test by adjusting the test duration, number of threads and memory allocation.
- Detailed reporting: Provides detailed reporting, including the test duration, number of errors found and CPU usage during the test.
- Error checking: The software includes a feature that checks for errors in the CPU and memory while the stress test is running.
- In-depth analysis: Provides in-depth analysis of the stress test results, including information about the stability of the system and any errors that may have occurred.
- Monitoring hardware parameters: Able to monitor hardware parameters, such as CPU speed, voltage and memory frequency while the stress test is running.
- Multi-thread support: Supports multi-threaded testing, which allows users to test multiple threads at once, increasing the accuracy of the stress test.
- Real-time graphs: Includes real-time graphs that display the CPU usage, temperature and other hardware parameters during the stress test.
- Save and load test configurations: Users can save and load test configurations for future use, making it easy to run the same test again at a later time.
- Temperate monitoring: Allows users to monitor the temperature of the CPU and other components to prevent overheating.
- Test specific parts of the CPU: Allows users to test specific parts of the CPU, such as the floating-point unit or integer unit.
- Torture test: Includes a «torture test» mode that runs an intensive stress test for an extended period of time to find stability issues.
- Workload distribution: Uses intelligent algorithms to distribute the workload across multiple cores and threads, ensuring an accurate stress test.
Compatibility and License
Prime95 is provided under a freeware license on Windows from benchmark software with no restrictions on usage. Download and installation of this PC software is free and 30.8.17 is the latest version last time we checked.
Mersenne Research accepts donations for the continued development of this free software.
What version of Windows can Prime95 run on?
Prime95 can be used on a computer running Windows 11 or Windows 10. Previous versions of the operating system shouldn’t be a problem with Windows 8, Windows 7 and Windows Vista having been tested. Windows XP is supported. It comes in both 32-bit and 64-bit downloads.
- Prime95 Download
- Free Benchmark Software
- Prime Numbing Software
performance — What is Prime95 benchmarking?
8 years, 8 months ago
I’ve recently had to benchmark the CPU performance of a variety of operating systems on identical machines. I’ve been using the ‘benchmark’ functionality of Prime95 to obtain a consistent test. I’ve gotten some unexpected results such as Windows 2012 performing significantly worse than Windows 2008. It’s prmpted me to wonder what Prime95 tests actually do and what I can infer from my results.
There appear to be two distinct phases to the test. Phase one appears to use one of what Prime95 calls a «Worker» but does so using a various numbers of threads. Looking at activity on my CPU I can see that each core is being used fairly evenly. Here’s a graph:
The orange line is a normal Windows 2012 machine and the blue line Windows 2008. The grey line is Windows 2012 with hyperthreading enabled. As you can see Windows 2012 tails off significantly as the tests become more intensive.
Phase two appears to be the same as phase one except for the the idea that it benchmarks «multiple workers to measure the impact of memory bandwidth.» Here’s the corresponding graph for this test:
Phase two, however, doesn’t quite marry with the results from phase one; Windows 2012 doesn’t tail off as it did before and the hyperthreaded install is better even than Windows 2008.
My question is, what operations is the Prime95 benchmarking tool undertaking and what sort of factors might come into play to deliver the results I’m seeing?
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How to use Prime95
Prime95 is a free utility for testing the stability of your PC or laptop. Developed by George Woltman when creating a distributed computing project (when one equation is solved by several processors at once, distributing tasks among themselves). The main advantage of the application is that it occupies a minimum of memory (only about 6 megabytes), does not require installation in the system, while supporting processors of any generation.
The program comes in the form of a portable utility. That is, along with it, the folder contains all the system libraries necessary to run it. Therefore, you do not need to install the application.
It is enough to unpack the archive downloaded on the official GIMPS website (the name of the project created by Woltman) and run the executable file (with the .exe extension). The program does not add any entries to the registry, does not create a cache and temporary files in user folders. However, some features require Internet access.
The utility supports all current versions of Windows (starting from XP), there is also an assembly for Linux distributions. Processor testing is performed by calculating prime numbers using the Mersenne formula.
How to use Prime95
When you start the application, a dialog box appears asking you to:
- Join the GIMPS project. That is, all calculations performed will be used to search for new prime numbers using Mersenne algorithms. An internet connection is required for this feature to work.
- Run a basic processor stress test.
This test uses all of the CPU’s resources and can become very hot. It is recommended to run a program for monitoring CPU temperature in the background (for example, AIDA64 or HWMonitor). When heated above 85 -90℃, the test should be stopped.
If you opt out of joining GIMPS and running the basic stress test, a new «Run a Torture Test» dialog box will open. The following settings are available there:
- Small FFTs test start. The search for new numbers is done using only the processor’s cache. That is, RAM is not used at all.
- In-placelarge FFTs. A test using the processor cache and a small amount of RAM (about 32-64 megabytes).
- Blend. The key difference is the use of all available RAM to speed up calculations.
- Custom. Customizable testing mode.
In the latest versions of Prime95, a processor test using the Medium FFTs algorithm is also available. In this mode, all processor caches are used, including L4. This allows you to test the latest CPUs with 16 or more cores (including server or motherboards that provide the ability to install multiple processors at once).
Running Custom Troture Test provides the most functionality for the user. Therefore, it is recommended to work in this mode. You can also launch it from the «Options» tab. The following settings are recommended:
- Min and Max FFTs size should not be changed (or set to the maximum available difference). This indicates the range in numbers between which the search will be performed.
- Run FFTs in Place should be left blank. In this case, all cache memory and RAM are used. If you check this item, then all requests to the processor will be sent to the same addresses.
- Memory to Use. You should set the number of megabytes that will be available for Prime95 to perform calculations. It is recommended to approximately indicate the amount of RAM that is currently free (you can find out from the «Windows Task Manager»). If you set a larger number than the actual available RAM, then the paging file will be used.
- Time to run each. Here you can set the time that is allotted for the search for prime numbers for one order. It is recommended not to change the initial setting.
After pressing “OK”, the test will start directly. To stop the test, select «Stop» in the «Test» tab, select «Stop all tests» in the next dialog box.
In the main window, when testing is performed, general information about the system is displayed, namely: processor architecture and generation, cache memory size, test algorithm used.
Even in Prime95, a benchmark is available to check the performance of the system and compare it with other PC configurations (data about which are uploaded to the GIMPS website). To do this, select «Benchmark» in the «Options» tab, and then specify the maximum size of FFTs (it is recommended not to change, the default is 2048).
A number of users also have a question about how to use the log files generated at the end of the tests. Notices of errors received when searching for prime numbers are contained in the «Worker#1» section.
What to do if you encounter an error
The following are the most common causes of errors when testing your computer in Prime95:
- The operating system has forced a termination of the Prime95 application. This happens if the process has used up the entire resource of RAM and the page file. It is recommended to set the Memory to Use value to less.
- CPU overheating causing throttling.
- Damaged RAM.
- Errors in the operation of the multicontroller (or northbridge). Because of this, the exchange of data between the processor and RAM occurs with errors.
The application does not allow you to determine the exact cause of the errors. But when they appear, the first thing to do is to check the RAM using the Memtest86 utility. And then contact the service center for help.
Total: Prime95 is a small program that allows you to stress test your PC or laptop. It can be used to quickly check for hardware problems with the RAM, CPU, or Northbridge. It is also suitable for determining the maximum temperature of the CPU.
More about Prime95
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Of those who visit this site, there is hardly anyone who is sitting at a non-overclocked computer. Although the statistics state that the majority of users do not overclock their computers, the number of overclockers is growing, which is good news :). And if earlier overclocking was practiced as a means to combat the lack of resources, now there are more and more people for whom overclocking is something like a sport.
You don’t have to look far for proof: about a year ago I decided to buy memory heatsinks for my video card; after a long search, I realized that I would have to make them myself. However, over the past couple of months, the situation has changed radically: after shopping, I get the impression that a non-ferrous metal smelting plant has begun to work for our needs :). Even a store has opened that deals ONLY with overclocker accessories: there you can buy almost everything that you read about on the Internet (For those who are in Kiev: the store is called «Eletek»). The soul rejoices when you think about all this.
But the material base is, of course, good, but theoretical knowledge, as for me, is perhaps more necessary. Of course, there are people who know (or think they know :)) everything about overclocking, but most beginner overclockers have a lot of questions. And people who have a solid stock of knowledge in this area may also not know something. I decided to do my bit in resolving the issue of achieving maximum stability (what a hackneyed topic …).
Of course, in the arsenal of every self-respecting overclocker there is a decent amount of programs with which he checks his machine for stability. The trouble is that there is no such program that could test a computer and say for sure that yes, the system is one hundred percent stable … One program can spin without failures on an overclocked machine for an infinitely long time, while another falls out almost immediately . Most of these programs give errors only on VERY unreliable computers, but even here it came to curiosities: on the Internet you can find one once quite popular stability test, I remember it because it managed to work without failures even on a system with a heavily overclocked processor. I don’t know how he managed it, but on a computer where he could easily work for many hours without finding any errors, most games crashed after a few minutes.
You can spend as much time testing your computer as you want, tormenting it with dozens of different tests, but the moment when you can say that the computer is 100% stable will most likely never come. In addition to this drawback, which is typical for the vast majority of tests, I will note a few more: most specialized programs for testing the processor do not inform the user about the error found, basically the testing program either falls out on its own, or the computer hangs or goes to reboot. Many complain about the fact that it sometimes takes a lot of time to test a computer with these programs … Due to freezes and subsequent «cold» reboots of the computer, information loss on the hard drive is possible, especially if the FAT32 file system is used.
But the article was not written at all in order to sow pessimistic moods among overclockers :). I want to inform you about the existence of a test that is strikingly different from its counterparts. Based on my four years of experience using the program, I can say that his diagnosis can be trusted in most cases. The authors of this program guarantee 100% system stability upon successful completion of the test. I have always been skeptical about such statements, but practice has shown that there are very few exceptions to their statement. This test tested a huge number of systems (I worked in computer clubs and computer assembly companies; out of interest, I overclocked everything that could be overclocked :), both overclocked and at the nominal frequency. On the computers tested by this program, I later ran all the tests known to me, and after a couple of years I concluded that the program rarely makes mistakes.
Her name is Prime95, and there are a lot of links to her on the Internet. The speed of the software is impressive: on some unstable systems, where 3Dmark seems to run without problems, Prime reports an error within the first 5-10 minutes (especially on systems where the «bottleneck» is a weak video card, and 3Dmark cannot check such a system . ..).. Prime in a few hours finds those errors that, perhaps, would never have made themselves felt. Softina is also good because it stops testing if it fails, giving a message about a problem that has appeared, while even solidly overclocked computers do not hang, and therefore, you don’t have to worry about the hard drive. The unpopularity of this program among overclockers can be explained by the fact that it was created for completely different purposes (its main task is to «draw» one hundred thousand bucks, I’m not joking, for those who are interested — read the Help for the program) and checking for stability is one of its many features .
The principle of operation is quite simple: the program performs calculations, the result is compared with the reference (previously known) on the disk; if they don’t match, Prime reports an error. Prime does an excellent job of checking the stability of the processor, L1 and L2 cache, memory and motherboard. Unfortunately, it will not answer the question which of the above caused the failure; this is up to you to figure out. Prime is optimized for most processors, and will load (and therefore check) all the execution units of your stone when running. Those who need a completely stable system will have to drive Prime somewhere around 5-6 hours. More than 24 hours is pointless to check, and I think no one will wait that long.
How to use? After installing Prim, in the window that appears, click the «Just Stress Testing» button — that’s it, the program is ready for use. The interface of the program is extremely ascetic and, especially at first glance, is not intuitive :). But don’t let that bother you, it doesn’t affect functionality in any way. We have the following menus: «Test» «Advanced» «Options» and «Help». Oddly enough, the function we are interested in is not in the «Test» menu, but in the «Options» menu. By clicking on it, the first thing we see there is the «CPU …» item. Here you can see if your stone was determined correctly, you do not need to specify the amount of free memory: this is necessary for other purposes that we do not need. The next item is «Preferences»: the «Minutes between disk writes» function may be of interest here; by default, the program keeps a log file (results.txt in the folder with the installed program), where it writes the current status of the check. I recommend setting the minimum value to 10 minutes — this is our black box (computer freezes, brother accidentally turned it off, etc.).
And here is the «Torture Test» menu that we are interested in: its name alone makes you shudder :). Well, let’s click… Now you should specify in which mode the test should be run. Options: «Small FFTs» — the data is placed in the cache, theoretically checks only the processor, without affecting the memory. In practice, this is not always the case: if your memory does not hold the timings or frequencies you set (even if the processor is absolutely stable), then Prime will still give an error message, it will just take longer to find the error than when passing the test offered by default . The next mode is «In-place Large FFTs»: maximum heat dissipation of the processor, warms it up quite well, but for this purpose there is a more efficient CPUburn utility package. If the stone is to blame for the instability, then the error message will appear a little faster than when passing the default test. Then we see the default mode, «Blend» — in this mode, and I advise you to check your computer.
When this item is activated, Prime tests all available memory and processor. The best option for checking when it is not known what exactly is failing (during the test, either the memory or the processor is dynamically loaded). The «Custom» item is not needed yet (when you need it, you will know more about Prime than me :)), it is needed if you want to change some test parameter. Perhaps questions will be raised by the built-in benchmark: an almost useless function, highly dependent on the amount of cache and memory bandwidth.
So, I didn’t seem to forget anything. ALWAYS remember the rule of any overclocker: testing must be comprehensive!!! The test is best run at the same time as any other CPU-intensive program (3Dmark and all sorts, quake3, etc. ), remembering to set Prim to 50% CPU time. You can also set the priority in the program itself: click on the «Advanced» menu, select the «Password» item, enter the password — «9876». Do not ask why the password, I do not know. In our tab, the «Priority» item has become active, the value «1» is the lowest priority, «10» is the highest. Enjoy. Owners of stones with activated HyperThreading MUST run a second testing program together with Prim, no matter which one — the main thing is that it loads the second «processor». Otherwise, with an unstable system, you will have to wait much longer until an error message appears.
Run the test, wait: if 5-6 hours have passed, and the Prim’s icon has not turned yellow, (yellow icon => test stop => error message => unstable system), then accept my congratulations: your system (processor — motherboard — memory) — the «standard» of stability. Do you remember that no test can be completely trusted: of course, the program has never let me down, but where is the guarantee that it will not let you down? I believe that the probability of this is very small, but still, do not flatter yourself . .. After all, there are still a large number of factors that affect the stability of the system and which must be taken into account when overclocking.
I will give one example where the test we are considering is powerless. The developer honestly warns that Prime does not check the stability of the PCI and AGP buses, everything that is tied to these buses, as well as peripherals. Do not forget about such «pleasant» things as exceeding the PCI and AGP frequencies on many motherboards when overclocking via the bus and, as a result, possible failures when working with the hard drive, integrated sound, PCI devices, video card, etc. If there is a function of fixing the frequencies of these buses in the BIOS, we activate it.
We figured it out… If the test gave the message «FATAL ERROR: Rounding was 0.5, expected less than 0.4» and so on… Here you can definitely say that your system is not working reliably and somewhere there was a hardware failure. Do not console yourself with thoughts like this: «. ..because everything works stably for me… …stupid program, raw, glitch on glitch, I’ll erase it and live in peace…». I myself was often driven to madness by Prime by unexpectedly knocking out on supposedly stable systems, but not once did I dare to doubt the reliability of his diagnosis. Let this error not appear now, but someday at the most inopportune moment it can still emerge. Let’s not be like those unfortunate overclockers who «stable work is the work of an overclocked device, in which glitches and malfunctions appear no more than once every five minutes» :). I hope you know what can cause instability and how to deal with it. Experiment on health. Note: The faster Prime reports an error, the more unstable your system is.
I’ll describe a couple more situations that I have encountered and that you may encounter. I recently replaced my 9600Pro with a 9800SE without broken pipelines and immediately ran into a classic problem, so to speak. The system was successfully tested by Prim and any other tests that do not use a video card; the video card was also in order, it passed the six-hour test at high resolutions with the Nature test (3DMark2001) without any problems, which, as you know, practically does not use processor resources. However, if you run 3DMark in high resolution and BURNP6 (Prime) at the same time, the computer instantly hung :(. The problem was eliminated by lowering (below nominal) the frequency of either the video chip or the processor and completely disappeared only after replacing the power supply. Although, according to the readings of the motherboard, the voltages produced by the power supply were within normal limits.. Given as an example, remember that these symptoms do not unambiguously indicate the power supply, it is just the most likely culprit.0003
Another nuance: a processor that works stably at a certain temperature may malfunction when it rises, each processor has its own temperature threshold, you can find it out using Prim and a hair dryer :). It happens that a stone at the same (at least, so the motherboard claims) core temperature works stably with one cooler, but not with another (for example, a review of the «Gigabyte 3D Cooler-Pro» cooler by Doors4ever). Perhaps the reason is poor contact between the processor core and the heatsink, or it may be the poor thermal conductivity of the material from which the heatsink is made and it does not provide effective heat removal from the processor.