is it possible to underclock a atmega328pu 20mhz chip to 16mhz?

hi is it possible to underclock a atmega328pu chip to 16mhz?

Yes. That is what the Arduino Uno does. You can underclock the AVRs all the way down to zero Hz, as far as I know. (A stock Atmega328p-pu runs at 1MHz, using an internal 8MHz RC clock with an additional divide-by-eight.)

so i just put an16mhz crystal there?

Yup - just take off the 20mhz crystal and put on a 16.

You'll have to reburn bootloader afterwards if it has a bootloader built for 20mhz on it (else the serial baud rate will be wrong and you won't be able to upload to it).

thank you for the reply