Prime95
Prime95 gives overclockers accurate CPU and memory stress testing using GIMPS prime-search workloads. Based on the Lucas-Lehmer Test, it helps diagnose instability under extreme load. Download Prime95 now from our website and learn how to use it.
What is Prime95?
Prime95 is a free utility that stresses your CPU by running heavy math calculations designed to test real-world stability. It’s used for testing computer stability and supporting the Great Internet Mersenne Prime Search (GIMPS) project. The software runs intensive mathematical workloads that fully load every CPU core, making it one of the most trusted stress-testing tools for builders, overclockers, and anyone checking system reliability.
Prime95 uses GIMPS workloads based on Mersenne primes (numbers of the form 2^p − 1) and relies on Lucas–Lehmer and PRP tests. These integer-based FFT operations form the core of the Prime95 test. They place extreme stress on the CPU and memory, helping overclockers detect instability caused by poor cooling, unstable voltages, or RAM issues. It also contributes to GIMPS’ search for new large prime numbers (for mathematical research).
The program includes the well-known Torture Test, offering presets that focus on the CPU, memory (RAM), or a balanced load. If a system fails Prime95, it usually indicates a stability problem worth fixing. The latest version of Prime95 is multi-threaded, automatically managing CPU cores for full stress testing. It also introduces PRP proofs, new resource limits, and improved verification processes. Whether you want reliable stress testing or wish to contribute to GIMPS Prime95 research, you can download the latest version from our Prime95 official website.
Things to Know About Prime95
Here are key details of the top CPU stress-testing utility trusted by system builders, overclockers, and GIMPS contributors:
Download Prime95 [Latest Version]
Prime95 || v30.19b20 || 8.4MB
For Windows
- Operating System: Windows 64/ 32-bit
- Version: 30.19b20
- Size: 64-bit: 8.4 MB, 32-bit: 7.1 MB
- Released Date: 2024-06-02
For Linux
- Operating System: Linux 64-bit/ 32-bit
- Version: 30.19b20
- Size: 64-bit: 5.6 MB, 32-bit: 4.5 MB
- Released Date: 2024-06-02
For Windows Service
- Operating System: Windows 64/ 32-bit
- Version: 30.19b20
- Size: 64-bit: 6.7 MB, 32-bit: 5.7 MB
- Released Date: 2024-06-02
For Mac
- Operating System: Mac OS X 10.9 (Mavericks) or later
- Version: 30.19b20
- Size: 4.3 MB
- Released Date: 2024-06-02
For FreeBSD 12
- Operating System: FreeBSD 12.0 (64-bit)
- Version: 30.19b20
- Size: 5.9 MB
- Released Date: 2024-06-02
Source Code
- Operating System: Windows, Linux, FreeBSD, and Mac OS X
- Version: 30.19b20
- Size: 38.8 MB
- Released Date: 2024-06-02
Windows Service 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.
How to Download and Install Prime95 (Setup Instructions)
Prime95 works on Windows, macOS, Linux, and FreeBSD. It does not use a traditional installer; you simply download, extract, and run it. GPU software such as Gpuowl, mfaktc, and Mfakto is listed separately, but it is not required for Prime95 setup. Follow these steps if you are installing it for the first time.
Download the Correct Version
On our official Prime95 download page, pick the build for your operating system. You’ll see options for:
- Windows 32-bit and 64-bit
- macOS command-line build
- Linux and FreeBSD (.tar.gz archives)
- Source code (Prime95 source code bundle for manual compilation)
Download the Archive
Click the download link for your operating system. With Prime95, you’ll get:
- ZIP file on Windows
- TAR.GZ archive on macOS/Linux/FreeBSD
Save the file somewhere easy to find.
Extract the Prime95 Folder
Prime95 runs directly from its extracted folder.
- Windows: Right-click the ZIP, click on Extract All, and open the new extracted folder.
- macOS/Linux/FreeBSD: Use Terminal and run tar -xzvf filename.tar.gz for extraction.
After that, you’ll see the prime95.exe (Windows) or mprime (Unix) executable on macOS, Linux, and FreeBSD, plus support files.
Run Prime95
How you open and run the program depends on your OS:
- Windows: Open the extracted folder and run prime95.exe.
- macOS: Open the extracted folder and run the command-line executable in Terminal.
- Linux / FreeBSD: Run the program from Terminal using the command: ./mprime -m
The -m switch opens the menu interface, which makes setup easier for first-time users. At first launch, Prime95 will ask a few quick questions. This is normal and part of the initial configuration process.
PrimeNet Setup (Optional)
Prime95 will ask if you want to connect to PrimeNet. If you want to participate in the GIMPS project, enter your UserID when asked. Creating a UserID on the GIMPS site lets you:
- Track workloads
- View stats
- Manage multiple devices
You can also skip this and choose “Just Stress Testing” if you’re using Prime95 as a hardware test.
Confirm the Program Is Running Correctly
Once configured, Prime95 will connect to PrimeNet (if enabled), request work, and begin operating based on the selected settings. On Linux and FreeBSD, the program can also be configured to run automatically on system restart through standard service methods. On Windows, you’ll have to go to options, click on “start at bootup or start at logon” if you want Prime95 to launch automatically when you sign in.
Upgrade Instructions for Existing Users
Already have an old build of Prime95? Follow these steps to upgrade Prime95 without interrupting your ongoing test progress:
Step 1: Download the Latest Build for Your Device
Go to our Prime95 GIMPS download page and select the newest version for your operating system. Pick 32-bit or 64-bit according to your system.
Source code users can download the updated package as well.
Step 2: Stop the Current Program
Close Prime95 or mprime completely. Exiting the software does not interrupt your current work, and your progress is saved automatically. This step prevents file conflicts when upgrading.
Step 3: Install the New Version
Extract the downloaded files and copy them into your existing Prime95 folder. When prompted, confirm that the old files will be overwritten. Your existing configuration, userID settings, and active workloads remain intact, even if a test is mid-progress.
Step 4: Restart Prime95
Launch the new executable (prime95.exe for Windows or ./mprime for Linux/FreeBSD/macOS). The program continues your work seamlessly and preserves your previous settings.
Step 5: Review New Features
Version 30.19 of Prime95 adds faster Edwards ECM curves (speeding up factor searches), stage-2 ECM resume support (allows GPU-assisted factoring to continue seamlessly), improved timestamp tracking (better monitoring), and advanced PRP/LL work options. Compared to older versions, it enhances PrimeNet coordination, resource efficiency, and overall prime-testing performance.
How Prime95 Works?
Prime95 works by running heavy math workloads from the GIMPS project. It uses the Lucas-Lehmer test to check huge Mersenne numbers (2^p – 1).
These calculations rely on Fast Fourier Transforms (FFTs) that load every CPU core, the cache, memory controller, and RAM at the same time, so any weakness in cooling, voltage, or hardware shows up fast.
The Torture Test offers Small FFTs (pure CPU), Large FFTs (RAM and memory controller), Blend (full system), and Custom modes, plus a built-in benchmark for tracking performance.
How to Use Prime95 for a CPU Stress / Torture Test [Getting Started]
Prime95’s Torture Test mode pushes every core through heavy integer and floating-point workloads while exercising the L1, L2, and L3 caches. It surfaces instability fast, which is why it’s a go-to tool after an overclock, undervolt, or new build.
Before you start, install HWiNFO or HWMonitor and keep the sensor panel visible so you can monitor temperatures, voltages, and clock speeds throughout the run. Stop the test immediately if temperatures approach your CPU’s safe limit. Here are the basic steps to run the test:
For a complete walkthrough covering FFT profiles in detail, thread configuration, thermal safety limits, and how to interpret monitoring data, see our detailed guide on how to use Prime95.
Video Overview
Features in Detail
Prime95 includes a range of advanced functions that let users fine-tune testing, control workloads, and analyze stability with higher accuracy. Here are key features:
Core and Thread Targeting
Prime95 lets users assign tests to specific cores or threads. This helps isolate faulty cores, compare performance across CPUs, and check stability on multi-core or multi-socket systems. Affinity control gives precise control over how each worker operates.
Custom Memory Usage
You can set how much RAM Prime95 uses during Blend or Custom tests. This helps simulate real workloads, expose memory-controller faults, and check system behavior under higher memory pressure. Adjustable memory allocation improves accuracy during full-system stability checks.
Detailed Error Reporting
Prime95 records every computational error in structured logs. These logs help pinpoint failing cores, unstable voltages, or timing issues. Users can review error timestamps, worker behavior, and FFT sizes to identify patterns that reveal deeper stability problems.
Auto-Launch Configuration
Prime95 can start automatically when Windows boots. This helps long-term testers and high-uptime systems run continuous checks without manual input. It also supports unattended stability sessions for users who test hardware for extended hours.
Remote Control and Monitoring
This utility supports remote operation so users can adjust tests, view worker status, and track temperatures from another machine. This is helpful for multi-system labs, long sessions, and setups placed away from direct access.
Optimized for Modern CPUs
The tool fully supports today’s multi-core processors, high thread counts, and advanced cache designs. It distributes FFT workloads across all cores to expose thermal, voltage, and scheduling issues that only appear on newer architectures. This makes it reliable for testing current-gen hardware.
Why Choose Prime95?
People choose Prime95 because it pushes a CPU harder than almost any real workload, making it a trusted option for spotting hidden stability issues. Its Small FFTs mode hits maximum heat and power draw, helping users judge cooling performance under the toughest conditions.
Overclockers rely on it because passing a Prime95 run signals top-tier stability that lighter tests often fail to reveal.
Here’s how it compares and stands out from the most used CPU stress-testing tools:
| Feature |
Prime95 (Best Choice)
✔ Recommended
| AIDA64 | Linpack Xtreme | Intel Burn Test |
|---|---|---|---|---|
| User-friendly | Moderate | Easy | Moderate | Easy |
| Primary Purpose | CPU & memory stability | System info plus benchmarks | Extreme CPU/RAM stress | Quick stability check |
| Load Type | FFT-based synthetic load | Mixed realistic workloads | Dense linear algebra | Linpack-based high AVX load |
| Thermals | High | Moderate | Extremely high | Very high |
| Stability Testing | Best for long-run errors | Good for mixed-use faults | Finds instability fast | Detects issues quickly |
| Memory/IMC Testing | Yes (Blend/Large FFTs) | Partial | Yes | Partial |
| Configurability | High (FFT size, threads, RAM) | Limited | Limited | Minimal |
| Risk of Throttling | High with AVX | Low | Very high | High |
| Benchmarking | No | Yes | Limited | No |
| Cost | Free | Paid | Free | Free |
| Best For | Deep and long-term CPU and memory stability testing | Diagnostics and monitoring | Extreme overclock stress testing | Rapid stability checks |
Use Cases
Prime95 supports users who need absolute CPU reliability. These use cases show who benefits from its stress routines and how it helps validate hardware performance under demanding compute loads.
Overclocked CPU Validation
Prime95 helps overclockers confirm that higher clock speeds stay stable under sustained maximum load. Its Small FFTs routine exposes voltage issues, weak cooling, or unstable memory timings, so users can confirm their overclocked profiles can handle continuous pressure without hidden faults.
New PC Build Stability Checks
Prime95 helps builders confirm fresh systems run clean under heavy computational demand. It highlights cooling gaps, weak VRMs, faulty power delivery, or memory errors before daily workloads cause crashes. Easily decide if your new configuration is ready for long sessions.
Manufacturing and QA Stress Workloads
Hardware manufacturers use Prime95 to apply uniform, repeatable stress on CPUs and memory modules during burn-in. Its predictable routines help identify defective chips, unstable batches, and thermal issues before units reach customers.
Research and High-Load Computing Assurance
Prime95 supports users running scientific simulations, rendering tasks, or mathematical workloads by revealing how their system behaves under continuous compute pressure. Its GIMPS-based algorithms test sustained CPU performance so researchers and heavy users can confirm their system handles extended high-intensity tasks.
FAQs
Is Prime95 safe?
Is Prime95 free?
Where do I download Prime95?
Is Prime95 still a good stress test?
What is Prime95 used for?
Does Prime95 stress the GPU?
How long should I run Prime95 for?
Conclusion
Overall, downloading Prime95 provides the best way to see if your CPU and memory can handle extreme workloads. Originally made for mathematicians to test Mersenne primes, it now helps overclockers and PC builders check stability under heavy stress. It’s lightweight and pushes every CPU core for free. Remember to keep your system cool, watch temperatures, and don’t leave tests running unattended. Push your hardware to its limit and download Prime95 to verify real stability under heavy load. Enjoy!
