Guide: Stability testing with Prime 95
In this short guide I will explain how you can test the stability of your computer using the tool Prime 95. Overclocking causes instabilities at a certain point if you either reach the thermal or the electrical limit of your CPU. To see if your system is stable, Prime 95 is a very simple way to test.
First of all, you need the Prime 95 tool. Pick the version according to your operating systems:
You can also find different versions of Prime 95 in the Download Section.
The latest Intel CPUs feature the AVX instruction. Prime 95 27.7 and newer versions supports the AVX instruction which results in a higher load and core temperature. This will result in a lower overclockability, but a higher stability. However, almost no program or game can handle the AVX instruction. If you’re not using anything which features AVX, you can use Prime 95 26.6 without AVX so you might reach higher clocks.
Note: AVX only works with Windows 7 Service Pack 1 and newer.
It’s very important to keep an eye on the CPU core temperature. I recommend to use the tool Core Temp to check the temperature.
Once you got both tools ready, start Core Temp and check if you can see the temperature of all cores and if they make sense. On some AMD CPUs you will have odd values like a core temperature below the ambient temperature. This is not possible and if you experience this, check for a different tool to read out the core temperature. You can simply comment on this posting if you need help.
In the next step launch the Prime95.exe. You should now see something like this:
Click on “Just Stress Testing” to access the test settings.
Prime 95 comes with several different test options. Depending on which part of your system or CPU you want to test, you have to select the specific option.
I always recommend to use the “Custom” test with your own settings. The “Number of torture test threads” should be the same like like the threads of your CPU. For example if you use an i7-4770K with 4 Cores / 8 threads you should use 8 torture test threads. If you are unsure about the amount of threads of your system, simply open your taskmanager and count the amount of threads. Usually Prime95 detects the correct amount of threads and you don’t have to change it.
The correct torture test settings are important to test the right things of your system. These are the most important FFT sizes:
- 1344K: High load on the core and the core voltage
- 8K: Maximum heat production to test your cooling solution
- 800K: Test RAM stability
- 864K: Test the whole system
If you are overclocking your CPU, the first step would be to test the core clock. Set the Min FFT and Max FFT size to 1344 and check “Run FFTs in-place”. Also make sure that the time is set to 15 minutes.
Run this test for about 30 minutes to see if your CPU core is stable or not. Always check the temperature in Core Temp at the same time to make sure it does not exceed the maximum temperature of your processor.
Maximum recommended temperatures:
- Intel Haswell (E): 90 °C
- Intel Devils Canyon: 90 °C
- Intel Ivy Bridge (E): 90 °C
- Intel Sandy Bridge (E): 90 °C
- AMD Vishera / Bulldozer: 75 °C
- AMD Kaveri / Trinity / Richland: 75 °C
If it passed 1344K test for 30 minutes, you can either keep on tuning your CPU or go on with a full system test to see if it is 24/7 stable. Set the torture test to a Min FFT size of 8K and the Max FFTs to 4096K. Make sure “Run FFTs in-place” is still checked and the time is also still set to 15 minutes.
Prime95 will now run a full test in the following order:
448k, 8k, 512k, 12k, 576k, 18k, 672k, 21k, 768k, 25k, 864k, 32k, 960k, 36k, 1120k, 48k, 1200k, 60k, 1344k, 72k, 1536k, 84k, 1728k, 100k, 1920k, 120k, 2240k, 140k, 2400k, 160k, 2688k, 192k, 2880k, 224k, 3200k, 256k, 3456k, 288k, 3840k, 336k, 400k, 480k, 10k, 560k, 16k, 640k, 20k, 720k, 24k, 800k, 28k, 896k, 35k, 1024k, 40k, 1152k, 50k, 1280k, 64k, 1440k, 80k, 1600k, 96k, 1792k, 112k, 2048k, 128k, 2304k, 144k, 2560k, 168k, 2800k, 200k, 3072k, 240k, 3360k, 280k, 3584k, 320k, 4000k, 384k, 4096k
Usually this will take about 21 hours. So only run the full test if you really want to keep the settings for your 24/7 system.
If Prime95 simply stops running with an error, your system is most likely unstable. Raise voltages if you still have room in the temperature or lower the clocks.
You might also experience bluescreens during the torture test. The hex value in the bluescreen can be an indicator to find the issue. However these values might change from generation to generation.
- 0x00000124: Core clock is unstable. You need a higher core voltage
- 0x00000101: Input voltage (Intel Haswell) or Uncore (Intel Haswell)
- 0x00000050: RAM is unstable. Lower clock or raise memory voltage
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