8v on a 3.3v core, clocked to over 65Mhz speed AND the board still works at room temp after the experiment. I would love to see if the author would have been able to reach 100Mhz+ with a better/professional external clock.

Inspirational and thank you - За здоровье

Edit: Before I get corrected, the 328P core runs at 1.8v - 5.5v