Grats on the great OC on Haswell! (normally people get 4.6-4.7 tops , http://hwbot.org/hardware/processor/core_i5_4670k/
CPU-z isn't enough. You should try AIDA64 to determine stability .
Unvalidated stress tests are not advised ( such as Prime 95 or LinX or OCCT, Intel Burn Test or other comparable applications ). For high grade CPU/IMC and System Bus testing Aida64 is recommended along with general applications usage like PC Mark 7. Aida has an advantage as it is stability test has been designed for the Haswell architecture and test specific functions like AES, AVX and other instruction sets that prime and like synthetics do not touch. As such not only does it load the CPU 100% but will also test other parts of CPU not used under applications like Prime95. Other applications to consider are SiSoft 2013 or Passmark BurnIn. Additionally this generation has a more specialized point of consideration for synthetic stress tests. When using an adaptive vid voltage control will be automatically controlled by the iVR when a complex concurrent AVX load is initialized from Applications like Prime95 or Aida Or LinX more voltage will be supplied than has been defined/requested.
Step #4 Testing:
This is the most time consuming part of the overclocking procedure because stress testing takes up a lot of time. Users like to use Intel Burn Test as well as Prime95 to see if the CPU is stable, however AIDA64 also has a good stress tester which Intel recommends because it is more realistic and stresses the different CPU domains rather than just the cores or certain combinations. Stay under 90C full load when dealing with stress test programs like IBT, LinX, and Prime95, I would say 85C for AIDA64 stress tester which is what Intel recommends be used since it stresses more parts of the CPU. Stasio recommends using at least 512mb of memory in the preferences for AIDA64, even 1GB he says should be used to really stress the memory.
http://www.overclockers.com/3step-guide-to-overclock-intel-haswellEdited by AlphaC - 9/23/13 at 5:29pm
How to test for stability has been a very long and drawn out debate. Some people use Prime95, others IntelBurnTest, still others OCCT. I’m here to tell you whatever you want to do is fine, as long as you know their pluses and minuses. For instance, Prime95 only tests the one instruction set on your CPU but not all at once (SSE, AVX, FPU, etc). It’s good for heating up your CPU, absolutely, but it doesn’t necessarily throw the kitchen sink at it.
From the first 3770K and even at present, ASUS advocates using AIDA64′s stability test. The software is free (shareware, with just a couple features blocked; licenses are cheap if you find you need everything) and easy to use. The reason they advocate AIDA64 – with which I agree – is because it tests all instructions at once. It throws everything plus the kitchen sink at your CPU. It’s fast, stable and will also heat up your CPU. Thus, here is my tools list for testing stability.
* AIDA64 for stability testing.
* CoreTemp for core temperature monitoring. (Click “More Downloads” for the standalone 32- and 64-bit versions.)
* CPUz for frequency and voltage monitoring.
Alternatives to AIDA64
* OCCT (includes Linpack testing)
* Prime95 (Old school)
* IBT (Intel Burn Test)
Super important note: These programs will increase temperatures further than any other program you’ll ever use in day to day PC operations, even Folding@Home. So be sure to watch your temperatures. If you are seeing frequency and voltage throttling because your CPU is north of 95°C (or worse, north of 100°C), you need to dial it back. Even if your chip can clock that far, it’s not good to operate at the temperature of boiling water for prolonged periods.
How long you run for stability testing is totally up to you. After doing this for years, I tend to take the easy route – 10 minutes to an hour of stability testing, then cease that nonsense and use the computer for a week or so. If you want to immediately jump into mission critical work (i.e. writing word documents / editing spreadsheets you can’t lose, programming, etc…anything that you don’t want to potentially crash on you), you might want to do it longer than I. Rational people I know suggest 24 hours of stability testing before they’ll deem their overclocks stable. There are good arguments for doing it that long. Just watch your temperatures and make sure you’re not throttling.