We're going straight to page two of AnandTech's architectural review of Intel's Broadwell, jumping into the overclocking results. With Skylake rumoured at 5GHz on air cooling, something we still confirmation of, its predecessor architecture isn't particularly appealing.
In fact, from an overclocker's point of view Broadwell is appalling. The sample reviewed by AnandTech reaches a mere 4.2GHz on air cooling with 1.325V, disappointing to say the least. In Intel's defense, Broadwell was never meant to be be a full-blown desktop CPU and is more of an up-scaled mobile design. With its replacement Skylake coming tomorrow, there's no reason why we will need to bother with Broadwell anyway.
Check out AnandTech's overclocking review here. They also do a proper IPC comparison with hardware dating back to Sandy Bridge.