SLI - Must the Clock speeds be the same?

Hi, I have 2x gtx 670 asus directcu ii in SLI, I was wondering if using "precision-x" software, I should set em up to have the same clock speeds...

I've read somewhere that with the newer drivers around... the clocks don't necessarily synch anymore...

The reason I'm asking, is because I run them in SLI in a tight space, so I thought I'd give a more agressive OC on the bottom card (since it's always cooler than the top one) and a more mild OC on the top card, to help reduce the heat...

Only answer if you are certain about your claim pls.

(Side question: Since these cards use kepler boost, IF the clocks must be the same, must I take into consideration the Kepler boost, which is not exactly the same on both the cards... one card can achieve 30mhz kepler boost more than the other...)

 

Usually you'd want sync'd clock speeds for both cards. If one gets ahead of the other due to high clock speeds you could run into issues with stuttering in your games.