Tech Support Forum - View Single Post

**mattlock** · 01-30-2008, 02:59 AM

How to Stress Test Your Multicore Processor

This is a short guide explaining how to put a 100% load on Single, Dual or Quad Core CPUs using Prime95 version 25.6. This is not an official release as of 3-15-08.
This guide is written for PCs running Windows XP.

Prime is a program designed to find new Mersenne prime numbers but is great tool for testing the stability of an over clocked processor. The “Torture Test” in Prime95 compares the results of your computers calculations to known good results. An incorrect result shows as an error and means your system is unstable.

Prime95 stresses the most power/heat intensive part of a CPU subsystem, which is the FP unit. What that means is, while it can induce heavy loads otherwise not replicable in real-life work loads, there are many sections of cores which aren't tested for integrity with it. Hence, it is possible, although very rare, that something Prime95 stable is not stable at all - infact - very unstable. While this is very rare, the early releases of the AMD Phenom is an example of a processor that exhibited this behavior.

You can test stability further with general benchmarking, gaming and system running after Prime95 testing and that should show up all errors. Some systems suffer instability due to the sudden drop of load only. Some due to poor VRM's and Vdroop issues and others just because something in the system is unstable.

Now on to users guide.

Download the appropriate version of Prime95 from the links below paying attention to the download location and extract the file to its own folder. Navigate to the folder and double click the green Prime95 icon.

Upon first run, you’ll have two options “Join GIMPS” and “Just Stress Testing”. Choose “Just Stress Testing” and the “Torture Test” window will open.

Windows 32bit Version 25.6
Windows 64bit Version 25.6

Test Options:

There are a few options in the torture test, each is described below.

Small FFTs - Stress CPU (Fits in L2, not much RAM tested)
Stresses the CPU only

Large, in place FFTs – Stress some RAM (Max heat & power consumption.)
Use this option to see how hot your CPU will get. The max temp for CPUs vary from chip to chip, but a good rule of thumb is not exceed 60°c under 100% load. Most prefer to stay a little closer to the 50°c mark under heavy load.

Blend – Stress CPU and RAM (Lots of RAM tested)
Use this option to check the overall stability of your system. Many consider a system that can run the Prime95 blended test for 24hrs without an error to 100% rock solid.

Custom – Allows you to set the FFT sizes, the amount of RAM used, and the time to run each FFT.
This feature was handy when Prime95 was single threaded and required multiple instances running to load each core, because you could split the available RAM between each instance of Prime. Now that it is multi-threaded splitting the RAM is no longer necessary.

Once you have settled on your test simply hit “OK” and all your cores will be getting hammered in no time.

Now, click "Advanced" and in the drop down menu click "Round off checking" to ensure the program stops when it encounters an error.

Be sure to monitor your temps closely. You should be close to your Max Temp within 30 minutes of running Prime95 providing you have good case air flow. If not, the temp will continue to rise as the heat builds up inside the case.

If any of the tests stop due to an error then your system is unstable. If over clocking any components, you'll need to tweak your OC until you can run the blended test for 12-24hrs without error.

Following the steps in this article is done at your own risk. We are not responsible for any damages that may result from running this stress test on your pc.

A Special Thanks goes out to Kalim for his input on the guide.

01-30-2008, 02:59 AM	#1 (permalink)
mattlock Mentor Hardware Team Join Date: Dec 2005 Location: Ohio Posts: 4,183 OS: XP SP2, Win 7 Beta, Win 7 RC My System	Quad Core Stress Test How to Stress Test Your Multicore Processor This is a short guide explaining how to put a 100% load on Single, Dual or Quad Core CPUs using Prime95 version 25.6. This is not an official release as of 3-15-08. This guide is written for PCs running Windows XP. Prime is a program designed to find new Mersenne prime numbers but is great tool for testing the stability of an over clocked processor. The “Torture Test” in Prime95 compares the results of your computers calculations to known good results. An incorrect result shows as an error and means your system is unstable. Prime95 stresses the most power/heat intensive part of a CPU subsystem, which is the FP unit. What that means is, while it can induce heavy loads otherwise not replicable in real-life work loads, there are many sections of cores which aren't tested for integrity with it. Hence, it is possible, although very rare, that something Prime95 stable is not stable at all - infact - very unstable. While this is very rare, the early releases of the AMD Phenom is an example of a processor that exhibited this behavior. You can test stability further with general benchmarking, gaming and system running after Prime95 testing and that should show up all errors. Some systems suffer instability due to the sudden drop of load only. Some due to poor VRM's and Vdroop issues and others just because something in the system is unstable. Now on to users guide. Download the appropriate version of Prime95 from the links below paying attention to the download location and extract the file to its own folder. Navigate to the folder and double click the green Prime95 icon. Upon first run, you’ll have two options “Join GIMPS” and “Just Stress Testing”. Choose “Just Stress Testing” and the “Torture Test” window will open. Windows 32bit Version 25.6 Windows 64bit Version 25.6 Test Options: There are a few options in the torture test, each is described below. Small FFTs - Stress CPU (Fits in L2, not much RAM tested) Stresses the CPU only Large, in place FFTs – Stress some RAM (Max heat & power consumption.) Use this option to see how hot your CPU will get. The max temp for CPUs vary from chip to chip, but a good rule of thumb is not exceed 60°c under 100% load. Most prefer to stay a little closer to the 50°c mark under heavy load. Blend – Stress CPU and RAM (Lots of RAM tested) Use this option to check the overall stability of your system. Many consider a system that can run the Prime95 blended test for 24hrs without an error to 100% rock solid. Custom – Allows you to set the FFT sizes, the amount of RAM used, and the time to run each FFT. This feature was handy when Prime95 was single threaded and required multiple instances running to load each core, because you could split the available RAM between each instance of Prime. Now that it is multi-threaded splitting the RAM is no longer necessary. Once you have settled on your test simply hit “OK” and all your cores will be getting hammered in no time. Now, click "Advanced" and in the drop down menu click "Round off checking" to ensure the program stops when it encounters an error. Be sure to monitor your temps closely. You should be close to your Max Temp within 30 minutes of running Prime95 providing you have good case air flow. If not, the temp will continue to rise as the heat builds up inside the case. If any of the tests stop due to an error then your system is unstable. If over clocking any components, you'll need to tweak your OC until you can run the blended test for 12-24hrs without error. Following the steps in this article is done at your own risk. We are not responsible for any damages that may result from running this stress test on your pc. A Special Thanks goes out to Kalim for his input on the guide. __________________ Matt Everest-Thermal Paste Instruction-Power Supply Info-Sensorview PSU Calculator-Speedfan-Bench Test Help TSF Fight Disease. It's Free! Last edited by mattlock; 07-14-2008 at 11:45 PM.