Quote Originally Posted by rmteo View Post
It is poor engineering practice to operate a device outside of the manufacturer's specs - take a look at the graph above where it shows that the minimum voltage is 4.2V for frequencies >25Mhz.
But I am not an engineer

I look at the graph as showing the primary frequency.
I have not built anything to run on less than 3.3 volts. I do a lot at 3.3 though. Have for some time. Makes working with SD cards and other low power things much easier. One power supply.