Intel has announced that the Haswell series of CPUs would be a lot easier to overclock. Like previous generations, the chips would feature a base clock frequency of 100 MHz, however, on Haswell CPUs users will be able to change this depending on the model.
Previously, the base frequency would also be applicable to the other modules in the chip, such as the memory controller. The problem with that system is that a deviation of just 7 MHz would destabilize some of the other controllers, even though the processor would keep working fine.
Consequently, Intel has thought to let owners of '-K' series CPUs change the base clock frequency to values such as 125 MHz or 166 MHz, while the other modules such as the memory controller would still run on a base clock of 100 MHz. Non '-K' series CPUs would likely not have an unlocked base clock modifier, even though in the past users could overclock non '-K' series CPUs through altering the base clock without touching the multiplier.
Back to the present, the maximum multiplier value tied to a 100 MHz base clock will be 80x, and the maximum would be lower for the other base clocks. For example, the maximum multiplier for a 125 MHz base clock would be 64x, and the maximum for a 166 MHz base clock would be 48x. Either way, in all three cases the maximum CPU frequency would be no higher than 8.0 GHz.
It will be interesting to see if these changes will actually yield in higher overclocks.