Bit of a lottery with Haswell but personally I'd be disappointed if at least 4.4ghz was not achievable with 1.25v or less, I know anything above stock is not guaranteed but we pay extra for K chips for a reason, I've achieved 4.5ghz @ 1.2v stable and think you would have to be rather unlucky to get a dog of a chip that couldn't reach 4.4ghz but they are there. Agree 4.4 to 4.5 on average.