PC Computer CPU Stability Testing






PC Computer CPU Stability Testing

The guide explains how to run your CPU at full power. It also details how to crank up your graphics card and make it work hard.

If your system can handle running at 100% power for an extended period, without crashing or locking up, you'll know that any subsequent problems will be due to some type of *conflict* (either software- or hardware-based), but not the hardware itself.

Many factors affect the stability of your system, but the one we're concerned with here is heat. When your CPU runs at full power, the little sucker gets HOT.

Unfortunately, electronics hate heat. Heat inhibits the flow of electrons (electricity). All electricians know that current flows more easily through cold wires ..

.. which is why your CPU comes with a heat-sink & fan: components that are designed to remove and dissipate this heat.

This is also why processors on many new high-power graphics cards (GPU's) now contain heat-sinks and/or fans. Heck, even chipsets on some motherboards now ship with attached heat-sinks.


There are many ways to test the stability of your PC, because there are a variety of applications that will put a heavy load on your CPU, such as SETI@home and RC5. I have selected the following seven programs (all freeware):

The last two files are BIG. If you're still on a dial-up connection, have one of your broadband buddies download and burn them to a CD for you. Note: some people, such as those who make the MBM Temp Report Tool, recommend using the lite version of HotCPU Tester Pro.


  1. Download and install the Folding at Home (FAH) distributed computing client. FAH is a good program to help test your system's stability, because it will cook your CPU nicely.

    But the nasty critter configures itself to start automatically when Windows starts. This is bad. You don't want anything grabbing your CPU clock cycles without first asking permission, especially not 100% of them.

    It would be nice if FAH gave you the choice, during the installation, or initial configuration, whether or not to Start with Windows, like other distributed computing clients do, or at least provide a setting in the Preferences, where we could configure the program to our liking after it's installed.

    But alas, it doesn't. (Greedy coders from the scientific community assume you want to donate every available clock cycle, every time you start your computer.)

    So, after installing FAH, make sure that it is *not* running (shut it down if necessary). Then go to into Documents and Settings\All Users\Start Menu and delete the the FAH icon so that this program won't start with Windows.

    Also check the same directory path for your particular log-in. If your CPU usage jumps to 100% at start-up and stays there, you did not do this correctly.

    Note: I have v3.24. If newer versions give you the option to not Start with Windows, let me know, and I'll revise this step accordingly. If you want to know more about FAH, their FAQ is posted here.

    If you plan to run this program on a regular basis, in order to contribute your CPU clock cycles to the scientific community, I would recommend cranking it back to ~85%. You can adjust this setting from the Advanced tab of the Control Panel (found under Configure...) Also read this article from the Tech Report.
  2. Download and install the Prime95 distributed computing client (the *.exe, not the *.zip). Notice that some of the Advanced options have been grayed out. This is to prevent novices from hurting themselves. Under the Advanced menu, you will notice that the "Torture Test" and "Benchmark" options are grayed out. We want to use these options. So, enable these options by selecting "Password" from the Advanced menu and entering a value of 9876. Magic, huh?

    On the new Hyper-Threading Pentium 4 CPU's from Intel, Prime95 will run these CPUs at only 50% .. which is why we use other CPU hogs, such as Folding at Home. I asked George, who is in charge of Prime-95, if he planned to modify the code to take advantage of Hyper-Threading. His response:

    "In short, no. Hyper-Threading is not really 2 CPUs on one die. Prime95 uses the chip's one floating point unit so much that a second instance of Prime95 would not find many more FPU cycles to use. You could run a second Prime95 from a different directory, but to put a higher load on the chip try running an application that primarily uses integer operations."

    Joshua discusses Prime95 vs Hyper-Threading here.

    On 17November2003, the 40th and largest known Mersenne Prime number was discovered by a Chemical Engineering grad student using this program on a lab PC at Michigan State University. I think he won US$100,000. Over 200,000 people currently participate in the search for Mersenne Prime numbers.

    Mersenne Primes are special types of numbers named after Marin Mersenne, a 17th century French monk who studied numbers 300 years ago (without the aid of computers). This background info is nice to know, but not necessary.
  3. Most people already have Motherboard Monitor installed (compliments of Alex Van Kaam, from the Netherlands). But if not, download and install it. I configure it to display the following items in my system tray:

    System tray CPU percent usage (reading 100)
    CPU temperature (reading 122)
    Case/Motherboard temperature (82)

    If you have a Hyper-Threaded Pentium 4 CPU, you should see *two* instances of the CPU-usage indicator in your system tray. If you have trouble with its configuration, click the little "?" (question mark) in the upper right-hand corner for a comprehensive Help file. Alternately, for more specific question, Alex's forums are located here.
  4. Let's begin our test for heat dissipation by launching Folding at Home. You should see your CPU usage indicator jump and CPU temperature begin to climb. By defaultMotherboard Monitor will display new information every 10 seconds. You can modify this setting, but I suggest you leave it set to its default.
  5. Now let's launch Prime95 and select "Torture Test" from the Options menu. Can you feel the temperature in the room begin to heat up? Your CPU usage should be pegged at 100%. Your CPU temperature indicator should be climbing steadily. It should continue to climb until it reaches equilibrium temperature (where the heat produced by CPU equals heat removed by heatsink + fan).

    Your CPU temperature will eventually stabilize at its new equilibrium temperature. This value is dependent upon (among other factors) ambient temperature. In other words, the warmer the temperature of the room where you're sitting, the higher this new equilibrium temperature will be. Conversely, you will notice that it reads lower on cooler days, or when the air conditioning is turned on.
  6. If your CPU usage indicator is not reading 100% yet, fire up Motherboard Monitor’s Heat Up utility. This utility is enabled via MBM's Launcher tab (bottom-left corner).

    Simply click on the little green "+" (plus) sign and navigate to the Heat Up directory inside MBM5's program folder. Double-click on the file labeled: MBM5HU.exe. The program will appear in the top box. Click on this file to select it, and then select (below) the same temperature sensor number as the one you selected for CPU temperature (mine is #2). Note that MBM displays your sensors in numerical order. In other words, your #1 sensor will be displayed first.

    Set the Temperature at which this program should started to slightly above your CPU's current temperature (I use 100-degrees F). Set the Temperature at which this program should closed to something high (I use 150-degrees F), so it doesn't close until you manually shut it down. Click Apply and put a check in the Enable box. Click Apply again. Alex sent word to say:

    Hi Rad.
    A small flame appears in the system tray when the program (MBM5HU.EXE) starts. Clicking that icon will stop the program. The code is very simple:

    procedure THeatupThread.Execute;
    X: Real;
    if Terminated then Exit;
    X:=X /
    until 1=0;

    There are no menus or settings for it. Tis an endless calculation that goes on and on. It's not perfect in that it will run only 1 CPU on a dual-CPU machine. Feel free to publish the code. It could turn into a nice project as I am sure others could create even bigger CPU hogs.

    Regards, Alex

    [When you're done testing later, stop MBM's Heat Up utility by simply clicking on the file MBM5HU.EXE to select it, and then click on the little red "-" (minus) sign to remove it from the windows. Click Apply.]

  7. If your system can handle an hour of this, with these programs running, you're good to go. Most people let it run max'ed out all night. If you wake, and you're system is still running in the morning, you're phat.

    Burning PCFor Intel P4 CPUs, anything below a temperature of 120-degrees Fahrenheit (49-C) at 100% CPU usage is fine. Anything over 130 (54-C) would begin to concern me. The heat-sink guide posted much higher temperatures here. If you see flames shooting out of your PC ( ) call the fire department!

    .. which brings us to the subject of system cooling. You want to suck (via fans) cool air in the bottom/front, and blow (via more fans) hot air out the top/back. You'd be surprised how much a couple of good fans can help your system's stability.

    Some cases even contain what's called a "blow-hole" at the top. If your stability problems disappear when you remove the cover from your case and blow cool air on you motherboard with a big house-fan, you have heat problems. These problems are more likely during the summer, when the weather gets hot.

    Yanking the thermal pad off your CPU and re-installing it (the CPU) with some thermal paste (also called thermal compound and thermal grease) will usually lower your CPU's maximum operating temperature by a few degrees .. which is sometimes the difference between instability and stability.

    A comparison between these different thermal interfaces is posted here. Electronics produce heat, but they don't LIKE it. Seems hypocritical, huh?

  8. Shutdown FAH, Prime95 & MBM's Heat Up utility. Download and install the 3D benchmarks 3DMark03 (178-MB) and AquaMark (62-MB). Run them one at a time. These will test the stability of both your CPU *and* your graphics card.

    These two programs are fun to run because they generate such gorgeous graphics, especially if you have a current generation 3D graphics card, like one of the newer Radeons, for example [review].

  9. Download, install and run Sandra. Especially the CPU and RAM benches. Make sure everything performs as it should. This is more of a *performance* test than a stability test.

You can also try PassMark's BurnInTest Pro (download here), which comes with a 30-day demo. After that, they want US$49, but you'll be done with it long before then. See here for more:> PC Benchmarks. A look at the factors that affect PC stability is posted here:> PC Stability Factors.

Before closing, I want to mention <shameless plug> a few other Radified guides you might find helpful. For example: