Some leaked PDF files that have been shown on IDF make it clear that Haswell will be easier to overclock. Intel said improvements have been made to the way you can overclock Haswell, making the process similar to tweaking Sandy Bridge-E CPUs. Interesting to see BTW is that the core multiplier ratios will go up to 80 with Haswell, nice.

Haswell should be fairly similar to the say the Core i7 3820 (Sandy Bridge-E) as it will allow both multiplier based overclocking and base clock overclocking when multipliers are locked in. You will be able to tweak your baseclock by 5-7% at three different presents – 100MHz, 125MHz and 167MHz. The reason why Intel quotes only 5-7% variance at those presets is because too much BCLK changing can cause instability in the PCI-Express and DMI-PLL. It is good to know that you will be able to overclock the chips, not just the K versions. There will be three base frequencies to which a multiplier can be applied: 100 MHz, 125 MHz, and 166 MHz. Several uncore frequency ratios will adjust themselves to compensate, thus leaving their stability unaffected.

Haswell will get integrated voltage regulation too  brininging each CPU an integrated VRM controller. Unlocked “-K” chips remain to have an as they can reach 8 GHz record (subzero cooling) as their base clock multiplier for the CPU cores are higher than on the others, of up to 80.0x for 100 MHz, up to 64.0x for 125 MHz, and up to 48.0x for 166 MHz.

Memory overclocking is going to be popular with Haswell. Intel is to  offer support for 200 MHz steps up to 2.6GHz and 266MHz steps up to 2.66GHz on memory frequency. The maxed out memory data rate supported will be a nice 2.93GHz !