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Because your card is fabric overlocked 100MHz and because you will use for gaming I would not go on some higher overclock and you will not get much improvement in games if you push card from good overclock to very high overclock.
It would be good if you test one by one card and try to OC with EVGA Precision X 4.2.1 or Afterburner 4.0 and to check voltage necessary for some clock. You will go easy with +50 on GPU and than test with benchmark test, Firestrike, 3DMark 11, Unigine Heaven 4.0 and Unigine Valley 1.0 are usually what people use to test stability. If all test finish you will increase clock with +50 again. If your card after some time show instability, crash, freezing, you will try to add +50mV voltages. I don't know how much mV you have space for GTX760 but in most case after crash you will need max what software offer you for stability and if tests pass after that I think that would be highest possible.
Avoid any voltage mod and use only voltage available with softwares.
If you successful OC 100MHz over fabric OC I would not go any way over that.
But that would not be easy task to both cards work stable on such clock.
Video memory I think 100-150MHz will be good just to improve little memory speed.
Before you try any OC you will test on fabric settings both cards in same test on native resolution with highest settings, DX11.
3DMark 2013
3DMark 2011
Unigine Heaven 4.0
Unigine Valley 1.0
During testing try to keep fan speed on manual on 80%.
When benchmarks test finish and you confirm stability card need to prove self in gaming, that's hardest task usually and maybe you will need to drop clock little from game to game.
Other members will complement this with their tips, special people who are familiar with SLI.
Remember +50 on GPU > benchmark tests > +50 on GPU > benchmark tests until crash or artifacts, after you find max GPU Clock time is for memory but you will not get nothing over 150MHz, that's only to support GPU clock and maybe help for smoother gaming in some little percent if clock is not too high than effect could be opposite.
For max stable clock or max gaming stable clock in most cases you will need days or even weeks and several games to confirm stability.
post edited by Vlada011 - 2014/11/13 08:11:24