The new 2nd generation Intel® Core™ processor family, aka Sandy Bridge, architecture has changed the way you overclock your processor. With the first generation of Intel Core processors you were able to raise the base clock to overclock. If you were lucky enough to have one of the Extreme or K series CPUs with the unlocked multipliers, you could also raise the multiple to overclock. This meant that unless your motherboard did not support overclocking, you would be able to overclock your processor.
Although you can still overclock the 2nd generation Intel Core processors by raising the base clock, you will only be able to adjust the base clock by 7-8%. This means in order to overclock the 2nd generation Intel Core processors to their limit, you need to have a processor with an unlocked multiplier. The unlocked processors are denoted by the K at the end of the processor model, such as the Intel Core i7-2600K. If you do not have a K series CPU you will be limited as to how far you can overclock. With the Core i5 and Core i7 non K series CPUs you will only be able to raise the multiplier by 4 and the base clock by 7-8%.
You are still able to overclock your memory whether you have a K series processor or not. The options for 1600MHz, 1866MHz and 2133MHz are available on most P67 based motherboards. The option for 2400MHz is also present on some ASUS motherboards, although we have only been able to run at speeds nearing 2300MHz in our tests.
The new Sandy Bridge processors are based on 32nm technology and are all rated under 100 watts. This combination along with the new architecture allows the processors to be overclocked to speeds that were only once achievable with exotic cooling, such as liquid nitrogen or dry ice. With an unlocked Sandy Bridge processor you are able to use CPU coolers, such as our Air Series™ or Hydro Series™ coolers, to reach frequencies over 5GHz! This was something that you were not able to do with the previous generation Intel Core processors.
To test how far we were able to overclock the new processors we used an Intel Core i5 2500K on an ASUS® P8P67 Pro motherboard. For cooling we went with our Hydro Series H70, to keep the processor cool while running heavily overclocked. For memory a 16GB Vengeance™ DDR3 kit was used, along with a Force Series™ F120 SSD, Professional Series™ Gold AX1200 PSU and a NVIDIA® GeForce GTX480 GPU.
During early overclocking tests we noticed that the multiplier seemed to have issues going above 45x. A few days after the initial launch of the processors, several motherboard manufacturers released a bios update that would help this issue. On ASUS motherboards the option to help this is called “Internal PLL Overvoltage”, when this is enabled it will help the processor run at higher multipliers. With this bios option enabled we were able to raise the multiplier up to 48x from the previous max of 45x. This allowed us to take the overclock from 4.7GHz to nearly 5.1GHz.
However the 1.57 volts required to reach this frequency is higher than what is considered safe for daily use. To find the 24/7 stable frequency the vcore was lowered down to 1.4 volts and the processor was able to run 4.9GHz for several days without any hiccups.
The new Sandy Bridge architecture has changed the way you overclock your processor and allows for some very high frequencies. Currently the fastest frequency achieved has been 5.79GHz using only air cooling. Although that is not something that would be stable 24/7, there have been several reports of processors hitting 5GHz for daily use using water cooling.