|Intel Core-i3/i5/i7 LGA1156 Overclocking Guide|
|Articles - Featured Guides|
|Written by Servando Silva|
|Tuesday, 24 August 2010|
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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 successfully run 30 hours of OCCT Linpack's test. I'm gathering all this 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 a 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 OCCT v3.1.0. Set it to run a pair of hours with medium data set and that will mean you'll have a PC stable enough to do heay tasks with the CPU. If you want to test maximum temperatures, CPU Linpack test is a must, since it loads the CPU higher than (almost) any other tool. Again, this tool isn't obligatory, but it's my favorite.
Since we're talking about 4 core CPUs here (Core i7 860), if I find OCCT failing after some minutes (or hours), 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. Both of these tools will let you test CPU stability and will also test RAM. 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 Prime95again and start Blend Test (uses lots of RAM). After a pair 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 you not to raise CPU vCore. You might want to give a read to our latest "Best CPU Cooler Performance Q2-2010" article to change you cooler to something a little bit more appropriate. My favorite temperatures 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 stucked 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 i5 655K 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. Of course, we must thank the 32nm manufacture's process, and Core i7 CPUs should be hotter than this.
You might be wondering which is the appropriate range of maximum temperatures. Have a look at the image above. If you add2 temperature" plus "Distance to TJMax" values, you'll find a TJunction value. For example: in this case 26+79 or 28+77=105. That's the maximum temperature you 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 Core i7 or the Core i5 750 processor, you might want to keep your temps below 80 degrees at full load (CPU Linpack OCCT test). Daily applications shouldn't stress it enough to pass 70-75 Celsius. For a typical Core i3/Core i5 Processor, temps should be lower, especially using a high-end heatsink like the one I used on my tests, which kept the CPU below 60 degrees at full load. Core i3 CPUs should be cold enough to be fairly overclocked with Intel's stock cooler, but try to keep your temperatures below 70 degrees. 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.