I don't know the default for the AXIA, but the max v will differ with each individual cpu. If you want to OC you should raise your multiplier and core in small increments. The voltage needs to be sufficient to allow the processor to run stably. Higher than necessary voltage will at least generate more heat, may prevent the cpu from working properly, and at worst destroy it. In any case, the life of the processor will be reduced with higher voltages.