d0 not any faster than c0 but more power efficient. although that efficiency of the d0 aloud the i7 to be able to go higher overclock than it c0 counterparts.
@PsychoSaysDie - Still not a bad clock though! It's luck of the draw with overclocking, isn't it? I know PCFormat once had a Q6600 that wouldn't go above stock, no matter what they did.