Just for more confusion :-)
An ATmega running at 16 MHz will accept a bootloader compiled for 20 MHz as well. It'll even run. But the baud rate will be very odd (115200 / 20 * 16 = 92160 baud). This baud rate thing is the entire reason why we need a different bootloader for each clock frequency.
An ATmega running at 16 MHz will accept a bootloader compiled for 20 MHz as well. It'll even run. But the baud rate will be very odd (115200 / 20 * 16 = 92160 baud). This baud rate thing is the entire reason why we need a different bootloader for each clock frequency.