then you should bump up the voltage to 1.25. if you get bsod then to 1.26, bsod again, then bump up to 1.27 and so on. The idea is to get the lowest STABLE voltage for the clock you want. If you use too much voltage, you will generate extra heat and shorten the lifespan of your cpu. Apply way too much voltage, then you are left with a $300 paperweight. The general max safe voltage for sandy bridge is 1.35. Since ivy bridge is essentially sandy bridge but more efficient, i think its safe to say 1.35 is max safe voltage for ivy bridge too. In my experience it has taken me 1.28 volts to oc my i5 3570k to 4.5ghz. So my guess since that i7 and i5 are similar, it will probably take around the same amount of voltage to oc the i7 to 4.5ghz. But every cpu is different so yea.
EDIT: fixed the grammer a little bit.