|Intel Sandy Bridge Overclocking Guide|
|Articles - Featured Guides|
|Written by Servando Silva|
|Wednesday, 20 April 2011|
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Processor Stability Testing
Before starting, I must say stability is a concept that can be perceived in different ways depending on your needs. While some people think SuperPi runs are enough to check stability, others want their PC to successfully run 30 hours of OCCT's Linpack test. I'm gathering all these concepts into a PC stable enough to do daily applications no matter how hard they are because that's what we're aiming for. I would be unsatisfied if my PC suffered a BSOD while doing multi-tasking, playing my favorite game online or coding and rendering the next-day's project. What you must understand, is that every component needs to be tested in different situations to check if it's 99.9% stable. In this case, since we're overclocking our CPUs (mainly), my favorite tool is Prime95. Run it through a Blend Test to check both CPU and Memory stability, or run in place large FTT for maximum heat and power consumption. Usually, a couple of hours means your PC isn't prone to suffer BSODs, but I prefer to leave it running at least 10 hours before working. Usually, a night running Prime95 should be enough.
Since we're talking about 4 core CPUs here, I usually fire up Prime95 and start doing Blend tests. Prime95 allows you to check which CPU core is failing, and so you can add voltage or compensate the CPU knowing which core is the weakest of all. However, if you're just starting to overclock your CPU, you might want to test it with something lighter, and Cinebench R11.5 is a good choice to ensure CPU is (at least) stable enough to boot into OS and open your OC tools. Even Cinebench uses all your available cores; it won't define any kind of stability by itself.
Next step would be testing your RAM. RAM is a little bit more difficult to test because while you can spend 10 hours running stability tests, it could fail while opening a very simple application (e.g.: Photoshop, MSN messenger, etc.). What I do is: start with MemTest and put all unused RAM to test until it reaches 100% (at least). Many people think this is enough, but RAM can be a real pain if you don't stress it enough. Try opening Prime95 again and start Blend Test (uses lots of RAM). After a couple of hours running Prime95, you might want to check with your daily applications and GPU benchmarks like Unigine's Heaven 2.1. Trust me; RAM fails exactly when you don't expect it to fail, so it's better to make sure it will be stable enough for hard daily work.One thing people hate is watching high temperatures on their PCs. If you're using Intel's stock cooler I would recommend that you not raise CPU vCore. You might want to give a read to our latest cooling articles to change you cooler to something a little bit more appropriate. My favorite temperature monitoring tool for Intel Core processors is Real Temp. This little application has a sensor test to check if any of your cores has a stuck sensor. I've also found this is very accurate software which is a MUST in this case. Below you can see an example of our Core i7 2600K at idle mode while Noctua's NH-D14 is sitting at the top of it. Ambient temperatures were below 25ºC, and our heatsink was good enough to keep it 1-3 degrees above ambient. The latest edition of this particular software offers CPU load and Power consumption readings. With these features we can isolate CPU power from all other components.
You might be wondering what the appropriate range of maximum temperatures is. Have a look at the image above. If you add "temperature" plus "Distance to TJMax" values, you'll find a TJunction value. For example: in this case 28+70=98. That's the maximum temperature your CPU will support before turning the computer off for self-protection. Of course, it's very unlikely to reach these temps, and motherboards normally have protection limits somewhere between 80-90 degrees. That's why it's actually very difficult to burn a CPU nowadays unless you're giving it too much voltage.
If you're overclocking a Sandy Bridge processor, you might want to keep your temps below 70-80 degrees at full load (Prime95 FTT test). Daily applications shouldn't stress it enough to pass 70-75 Celsius. Keep in mind CPU temperatures are meant to be kept below those limits at overclocking conditions. Thanks to the 32nm manufacture, you might be able to keep your CPU below 60 or even 50 degrees at factory settings (no OC, no extra voltage). Now that you've downloaded and understood your weapons, let's get a little bit more technical and analyze all the variables you should pay attention to while overclocking. In the next page I'll explain each variable and how to control it from your BIOS/OC utility.