Overclock of Haswell processors generation will be easier than their predecessors , in the motherboards settings menu users will be able to select the reference clock divider, stability will no longer depend on BCLK frequency , and the maximum multiplier increase to 77x . Thus, overclockers will be able to choose a combination of multiplier and BCLK frequency over a wide range.
Assocaite published overclocking result of the engineering model processor Core i7-4770K up to frequencies above 7 GHz. The overclocker wished to remain anonymous, used motherboard ASUS Maximus VI Extreme Edition Z87 chipset-based and the combination of 77x multiplier and BCLK 91.07 MHz frequency. You can see that CPU-Z utility has determined that the CPU voltage is increased to as much as 2.56 volts, but obviously this is a mistake.
Another overclocking Core i5-4670K to the frequency of 6.2 GHz (62x 100.5 MHz). In this case, a more recent version of CPU-Z correctly identified the voltage - 1.216 volts.
The third screenshot shows the ability of the processor Core i5-4670T to work with RAM, the effective frequency is increased to 3322.2 MHz: