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Ivy Bridge Overclocking

Computer enthusiasts usually believe that introduction of new manufacturing technologies should also improve the processors’ overclocking potential. In case of Ivy Bridge there are objective reasons to expect this: even the top CPUs in this family have lower power consumption, and the maximum temperature when thermal throttling kicks in increased to 105°C.

Moreover, there was also some hope that unlike their predecessors, Ivy Bridge processors could regain their ability to be overclocked by changing the base clock. However, there is no good news to report here: LGA 1155 platform requires unified clock frequency generator that shapes up the processor frequency together with the frequencies of the peripheral devices controllers and PCIe and DMI busses. So even with the newest Intel Z77 chipset any base clock deviation beyond the 105-107 MHz range causes a complete system failure.

Therefore, just as before the only way to overclock Ivy Bridge processors is by changing the clock frequency multipliers. They have a total of three multipliers:

  • Primary multiplier setting the frequency of the computational cored. It is fully unlocked in all K-series processors. All other processor models allow increasing it by four increments above the nominal.
  • Graphics core frequency multiplier, which allows speeding up processor graphics core in 50 MHz increments. This multiplier is unlocked in all CPUs.
  • Multiplier for the memory frequency. Ivy Bridge processors allow adjusting it in 200 MHz as well as 266 MHz increments, which allows using a vast variety of DDR3 modes.

There are not that many improvements over Sandy Bridge, but they are there indeed. The highest multiplier supported by K-series processors has increased to 63. Besides, it is now possible to overclock system memory in a much more flexible manner.

For example, this is what the list of supported DDR3 modes looks like for a typical LGA 1155 mainboard with an Ivy Bridge processor:

I have to say that the release of LGA 1155 platform has significantly simplified the overclocking process. Besides increasing the corresponding multipliers, all enthusiasts need to do is adjust a few voltages that affect the system overclocking potential.

Ivy Bridge processors, just like Sandy Bridge, have five voltages like that:

  • VCC - primary voltage of the processor computational cores. It directly affects the processor overclocking potential. For Ivy Bridge the nominal values are usually around 1.0 V or a little higher.
  • VCCAXG – graphics core voltage. Increasing this voltage helps raise the frequency of the graphics core integrated into the processor.
  • VPLL voltage. In most cases it doesn’t affect overclocking results, but comes in handy for setting overclocking records using extreme cooling methods.
  • VCCSA - system agent voltage. The nominal value for this parameter in Ivy Bridge is set at 0.925 V. By raising this value you can stabilize the processor memory controller when higher memory frequencies are in place.
  • VDDQ – memory voltage. Adjusting this voltage helps during memory overclocking, but you shouldn’t increase it beyond 1.65 V in order to avoid damaging the Intel processor.

Just like before, the only voltage, which pushes back the maximum stable CPU frequency, is the VCC. So theoretically, Ivy Bridge processors seem to be easy candidates to overclock.

Unfortunately, practical experiments uncover a few unpleasant issues. We tested two different Ivy Bridge processors in our lab, but none of them managed to achieve stability at the frequencies reached by their previous-generation predecessors. Using NZXT Havik 140 processor cooler we managed to overclock our Core i7-3770K processor only to 4.6 GHz.

…while Core i5-3750K processor was operational only at 4.5 GHz.

In both cases the CPU Vcore was increased to 1.2 V and Load-Line Calibration parameter was set to Ultra-High. Just like with other processors, increasing this parameter has a positive effect on the overclocking potential. However, it is important to keep in mind that excessive voltage increase may cause CPU degradation and failure. Therefore, while there is no real statistics on Ivy Bridge processors manufactured using new 22 nm process, we would like to warn you against using too high VCC values. Considering that the nominal voltage of the new processors is somewhere in the vicinity of 1.0 V, long-term use even at 1.2 V may have serious consequences. Therefore, we decided to refrain from any overclocking experiments at higher voltage settings at this point.

In any case, the frequency potential of the new Ivy Bridge processors turned out to be below our expectations. We didn’t manage to overclock them even to the same heights as the previous-generation Sandy Bridge. So, we can state that the overclocking potential of the newcomers has become worse, which may have been caused by the reduction of the geometrical die size of the new Ivy Bridge. Its overall size is 25% smaller than the Sandy Bridge die, and the computational cores have become only half the size of the Sandy Bridge cores. However, contemporary approach to processor die cooling doesn’t allow increasing the heat flow density in equal proportion, which causes local overheating of some parts of the processor cores during overclocking. High operational CPU core frequencies indirectly confirm that this problem indeed exists, although the processor cooler remained practically cold in this case.


Sandy Bridge (on the left), Ivy Bridge (on the right)

As a result, it looks like even after the launch of the new Ivy Bridge the title of the best enthusiast platform will go to LGA 2011. These processors not only boast additional features that allow overclocking them by simply raising the BCLK frequency, but also boast better overclocking potential. However, if the LGA 2011 platform seems financially out of reach, then the old Sandy Bridge processors may present a worthy alternative to Ivy Bridge. Especially, since they do not fall too far behind the newcomers working at the same clock speeds in computational performance.

 
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