Tuesday, August 13, 2013

[Article] Checking if your CPU overclock is stable

The most fun part of upgrading the CPU is overclocking. Of course, it is purely based on luck. You might get a CPU that can overclock wonderfully with low volts and low temps. And you might get a total piece of junk that needs a lot of volts and doesn’t overclock well. (I usually get that 2nd type of CPUs). They say it is silicon lottery. It’s a gambling man!

Temperature is your biggest enemy. In fact, when it comes to Haswell, temperature is your only enemy. To push the clocks higher, you need to up the volts up and that causes temperature to rise exponentially. Most people will have to max out at 4.2GHz on Haswell because of the heat. It’s mostly because of Intel’s crappy work using thermal paste in between the die and the heat spreader but there are other reasons too. Looks like they don’t want the enthusiasts to play with their silicon. Intel’s being naughty.

Say you have a good cooling solution and a good chip. Seeing those scores go up is nice and all, but making sure that your CPU is stable is very time consuming and pain in the butt.

But it depends. You can cheat a bit out of it if you want. You can either look for absolute stability or real-world stability. Failing in Prime95 doesn’t necessarily mean that you’ll ever get a crash (i.e. BSOD) with anything that you would normally do. I am more towards the absolute stability, but I don’t want to stress test for 24hrs in Prime95 with these summer heat.

Ironically, people have found out that sometimes even though Prime95 or any other popular stress testing app suggests that you have rock solid stability, you get crashes in games. So passing these stress tests doesn’t mean your are absolutely stable either.

So stability in my book means a combination of synthetic and real world tests as follows.

  1. Prime95 v27.9 Blend – no errors or BSODs for 6hrs
  2. Crysis 3 and/or Battlefield 3 – no crashes for 2hrs
  3. Handbrake H.264 encoding (one pass) – no crashes for 2hrs
  4. Asus Realbench – no errors or BSODs for 6hrs
  5. AIDA64 – no errors or BSODs for 6hrs
  6. Intel Burn Test: very high stress level – no errors or BSODs for 10 passes

If you can pass all these, then your overclock is stable. Out of all those, Prime95 is the most stressful. All others can pass, but Prime95 can fail with a higher chance. Most people will just run Intel Burn Test and say that their CPU is stable. But that alone is not good enough. Sure, you can say it is almost stable. I’ve been able to pass Intel Burn Test at 4.3GHz/1.22V but Prime95 would fail within seconds. Prime95 needed 1.24V to go on for 6hrs without a crash.

Ultimately, it is your choice. It’s your CPU, it’s your money paid, and it is you who use it. What if you can clock your CPU to 4.5GHz and get no BSOD and crash with the stuff you do with your PC and it fails all those synthetic stress tests? There is no harm clocking it up to 4.5GHz in that case.

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