How much can an Uno be overclocked?

Question

When running the board at room temperature (20 C) without any extra cooling mechanisms added, how much can the Arduino Uno be overclocked?

Also, what would I need to change/update to overclock the board?

Answer 1

With no active cooling, most ATmega328P will run at 30MHz but you will need to up the supply voltage to ~6V. I have never done this on an Arduino board, just an ATmega328P.

I provided an external clock from a signal generator.

The only way to achieve a speed faster than 16MHz is to change the crystal/oscillator/clock input for one faster than 16MHz.

As this was just an experiment, I didn't alter f_cpu in boards.txt, so all timers etc. would be incorrect. Baud rates would also be incorrect - the only way to upload code was to change back to 16MHz.