I dont understand, did the motherboard break? You must know to overclock such much ghz you need to up the voltage on your cpu... which means more temperature consumption. If the cpu can handle the voltage going up without reaching high temps then you can overclock to 4.3. If you overclock that much but dont get the voltage up a bit your machine will indeed restart or shut down because of it.
So , to overclock that much you need to set a higher voltage. I wouldnt mess with it if you dont understand very well what we are talking about. Maybe you should OC to 4.0 and try a high demanding game to max out the usage on the cpu. If that doesnt crash then you`re good.
Hope that helped out.