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Whenever you overclock a component in your system, you're eventually going to reach the limit of what it can do.
Stress testing is how you can find that limit. A stress test puts your system under an extremely hard load, so that if there's a problem, you'll find it now--rather than in the middle of a game.
In this guide, we'll go over how you can stress test your cpu, ram, and overall system (in a variety of situations).
However, before we get started, let's go over some of the common overclocking tools that can make overclocking and stress testing easier.
Monitor Important System Information with CPU-Z
CPU-Z gives you a lot of important information about your system, such as its current CPU voltage, speed, and multiplier. It also shows you the system's base clock rate ( BCLK), which is shown as Bus Speed in the picture below.
CPU-Z also has other tabs, such as Memory and Graphics. The memory tab is shown in the picture below. From there it's easy to see the RAM's frequency and timings.
If you're overclocking with turbo boost enabled, CPU-Z will not always be accurate for telling you what multiplier and speed your system is running at, since some of the cores are running with different multipliers and speeds, so just keep that in mind if you're trying to verify that turbo boost is working.
Keep an Eye on Your Temperatures with Core Temp
Stress testing and overclocking usually cause a lot of heat, so we need a way to make sure our temperatures don't get out of control.
If you're going to do any serious overclocking, you really need to have a better cooler than the stock heat sink and fan that comes with your CPU, so it's worth it to at least get a decent air cooler.
There are two things that cause your temperatures to rise: increasing the speed that it's running at and raising the voltage. Increasing the speed causes a linear increase in temperature, but raising the voltage causes the temperature to go up exponentially, so if you want to keep the temperature down, you really need to watch how high you let the voltage go.
A great program for keeping an eye on your processor temperature is Core Temp.
Core Temp shows you the current, minimum, and maximum temperature for each of your CPU cores (since the program started), so make sure it's always open when you're stress testing your system (to make sure the cpu doesn't get too hot).
Maximum Safe Temperature
Luckily, CPUs these days are made to take care of themselves--as long as the thermal monitor option is enabled in the BIOS, so if it notices itself getting too hot, it will slow itself down before it does any damage. This usually happens around 100 degrees Celsius.
However, it's still a good idea to keep your temperature close to what Intel expects it to be to ensure that it lasts. i7, i5, and i3 processors are designed to be able to heat up to around 72 - 74 C at maximum load and still maintain their longevity, so it's usually a good idea to stay below that for your everyday overclock.
If you're really trying to push the limits, I personally would not go higher than the upper 80s, and I definitely wouldn't use that as my day-to-day overclock, since you're likely to reduce the CPU life with temperatures that high.
Stress Testing Your CPU, RAM, and Overall System
There are numerous tools and software for stress testing your system, but the three best that I've found are Intel Burn Test, Prime95, and Memtest86+.
Each of them is good for testing specific parts of your system, so let's go over them now.
Important Changes when Stress Testing with Hyper-threading or Turbo Boost Enabled
The main change that you'll have to make (when stress testing fewer than all of your cores) is to change the number of threads that the test program uses. If you're overclocking with hyper-threading disabled, you'll want one thread for each core that you want to test, and if hyper-threading is enabled, you'll want two threads for each core that you want to test.
Both Intel Burn Test and Prime95 have options for specifying how many threads to use, so we'll point those out when we talk about both of them.
Use Intel Burn Test for CPU Stress Testing
Intel Burn Test (IBT) is what I use for stressing the CPU. It's an extremely stressful program that's based on Intel's Linpack for testing processors. It will make your CPU get very hot, so make sure you have a good cooling system in place. Also keep an eye on your temperatures in Core Temp.
With Intel Burn Test, you can specify the stress level of the test (how hard it stresses your system). There are four stress levels: standard, high, very high, maximum, and custom.
You can also specify how many times you want to run the test by changing the Times to run box and how many threads you want it to use by changing the Threads dropdown list.
Quickly Stress Testing Intermediate CPU Overclocking Steps
If you're just testing intermediate cpu overclocking steps (i.e. you're still trying to find your maximum overclock), it's fine to just run Intel Burn Test with a stress level of Standard and times to run set to 5 (as shown in the picture above). This should allow you to quickly test the CPU in a couple of minutes, which should be enough to bring out any obvious errors.
Thoroughly Stress Testing Your CPU
However, if you're testing the end result or an important overclocking milestone, I'd run Intel Burn Test with the stress level set to at least high and times to run set to 10.
Use Prime95 for BCLK, RAM, or Overall System Stress Testing
Prime95 is another stress testing program that can also be used to stress test the CPU, but I usually use it as a stress test for BCLK, the memory, or the overall system.
Before You Start, Enable Round Off Checking
However, before you do anything with Prime95, you should enable Advanced -> Round Off Checking (which is shown in the picture below). This makes Prime95 check for errors after each round, so you'll be notified if there's an error.
Once you do that, you can get to the torture test screen that you see below by going to Options -> Torture Test.
The Small FFT test is for testing the processor only, but I'd recommend just using Intel Burn Test for that, and the Blend test will test some of everything (cpu, ram, and chipset).
However, the Custom test will let you manually enter whatever settings you want. If you know what you're doing, the custom test can help you to zero in on a specific part of the system, so you'll be able to fail faster if there's a problem with the component you're currently overclocking.
If you're wanting to test fewer than all of your cores (or threads), just change the Number of torture test threads to run box (shown in the middle of the picture above).
Quickly Testing the Overall System
The custom torture test settings (that you see in the picture above) work really well for quickly testing how the overall system is working by sending large amounts of data between the cpu and ram.
You should run this test for at least five minutes.
You'll want to use this test when you're trying to
- Find your maximum BCLK.
- Test your ram's stability with the rest of the system.
Thoroughly Testing the Overall System
The blend test usually works really well for thoroughly testing the overall system.
I'd also recommend customizing this test to use 90% of your unused memory. You can do this by first clicking blend and then clicking custom (which will let you modify the normal blend settings).
To find how much of your memory is currently available, look at the Performance tab of the Windows Task Manager (as shown below). The amount of available memory is highlighted in red.
In this case 4358 MB is available, so we'd want to run the custom blend test with 4358 * 0.90 = 3922 MB of ram.
The amount of time you should actually run this test differs depending on who you ask. Some recommend a few hours is enough, and others say 24 hours is required to ensure stability under heavy loads (like 24/7 folding). However, most of the stable overclocking clubs require 12 hours to prove stability, so that seems like a happy median. I personally just run it overnight for about 8 hours, but run it for as long as you need to feel stable.
Test Your RAM with Memtest86+
Memtest86+ can be used to make sure your RAM speed and timings are stable.
Just burn it to a CD and boot your system from it. It will automatically start testing your memory and display a lot of useful information, which you can see in the picture below.
In each pass over your RAM, it runs a variety of tests, and if there's an error, you'll see an obvious red error message on the screen.
Best Practices for Memtest86+
If you're just testing intermediate RAM overclocking steps, I'd run at least 5 minutes or up to one full pass, to make sure your system is basically stable. And, once you think you've found your optimal settings, I'd recommend running at least two to three full passes.
This article is part of our ultimate overclocking guide: How to Overclock: Intel Core i7, i5, and i3 CPU Overclocking Guide.
If you're following along in the guide, you can get back to where you just were by clicking the link that follows: Understanding the Basics.