mattlock

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.

chauffeur2

Thanks Matt...I'll be the one doing this one.

mattlock

Good deal Dave. We'll get you some screenies soon. How do you want them, email, upload, imageshack link?

chauffeur2

email to me please whenever you're ready.

DonaldG

I'm having a look at it now Matt - I will post findings, queries an screenies as available...

DonaldG

Running Orthos & Orhos2

<twibat>!!!! I could have fried an egg on the processor!

I had to abort the test after only about 3.25 minutes because of exceeding the max temp of core 0 and core 1. Cores 2 & 3 were hot but OKish...

The graphs below is Celsius and the time scale is 1 reading a second...
The numbers at the bottom are seconds into the stress test...

I am surprised at the extremely rapid rise and fall, just a few seconds to hit the bell and to return to idle temperatures



Comments?

mattlock

For those interested, I replied to Donalds post in Folding heat problem & cooling thread

This article will be on hold until some further testing of the CPU affinity can be done.

JohnthePilot

I wanted to see the pic of Donald's machine taken in the dark.

mattlock

While this method will work to stress test quad core CPUs is not necessary any longer.

The latest releases of Prime95 are fully compatible with multi-core CPUs, and overall easier to to use. It auto detects the number of cores and sets the affinity itself. I will be revamping this guide to show how to use Prime95 to stress test a CPU as the primary subject and touch on the use of SP2004/Orthos as an alternative tool.

In reality, I think Orthos may have outlived its usefulness, since Prime95 can now be used on a single, dual, or quad without any additional setup required.

DonaldG

If you need 4 core screenies Matt, let me know exactly what...
(Assuming that I havent has a mini Chernoble inside the box!)

mattlock

Will do Donald. Here's a direct link to the 32bit version.

http://mersenne.org/gimps/p95v256.zip

When you open it choose just Stress Testing, and it will automatically open the torture test. Once the test is running you can stop/restart either by right clicking the tray icon or going to File inside the program.

BTW, it's an EXE no install required for torture testing.

JohnthePilot

Is that any different to the Prime95 torture test I've already used?

mattlock

It's a newer version, but I believe the only real difference is the support for multi-core CPUs.

Kalim

Matt: An internet search led me to this (1st page ) but you might want to change this. Orthos is now becoming absolete because it is extremely buggy and the new developer has taken over after 2004 and updated the old code many times, including the efficiency, the stress it places on each core and the speed of the benchmark code to develop Prime95 version 25.6. That's the best and most reliable now, it places a higher load than Orthos too and can choose the number of cores automatically in one application. ;)

Orthos is known to have a lot of bugs now. Mainly because it can freeze, error and reboot the system even when the system is fully stable (software bugs).

Small FFT to test CPU.
Blend to test bits of all CPU/Cache/Mem.

mattlock

It's been awhile, but I've editted the 1st post with the new article. The app is very simple and I'm not sure screenies are needed, but if you want them I have them. Just let me know. I am going to add a little to the end of the article in regards to temp monitoring.

@ Kalim

Thanks for the tip.
I actually stumbled across the latest P95 a couple of weeks after posting the Orthos article and stopped the presses on the Orthos work.

The Prime article is short and sweet, but I would love your input. Do you think anymore info is needed?

Kalim

Hey Matt :)

Only things I can mention are;

*/ Have this setting checked in Prime95 or it'll miss any calculation errors and keep going on even when it's in calculative error



*/ 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. I know of no processor which displays this behavior but, case in point, the new Phenom CPU's react exactly like this. They need many CPU sub-component tests to be verified stable.

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.

Would be nice to have screens if they aren't already being added

Great work though, those not at computers as often as us, really have no clue about these things - it's alien to them, so this helps them greatly.

mattlock

Dang!! Nice catch Kalim. I don't how I left that setting out of the print portion of the article....it's the third of seven screenies, that I have for the arty.

As for the second part, are the instabilities you speak of more overall system or CPU specific? I've was under the impression that Prime just tested the the stability of the CPU and, to some extent, the RAM.

I'll make some changes following your recommendations, and be sure to include the screenies. I'm pretty busy outside of the forum of late, but will get to it as soon as possible.

Thanks alot for your input, it is much appreciated.

Kalim

Nevermind, easy to miss bits out.

Instability is totally CPU related for the Phenom cases I mentioned, yes. Very strange though.

You're welcome