ATMEGA328P
I have recently compiled an Optiboot bootloader for the Atmega328P MCU driven by the 10MHz crystal and working at 115200 bps baud rate (8N1).
Instructions how to add this board to your Arduino IDE using the Boards Manager can be found here: https://github.com/impexeris/Arduino-Geiger-PCB/wiki
Instructions how to add this board to your Arduino IDE using the Boards Manager can be found here: https://github.com/impexeris/Arduino-Geiger-PCB/wiki
More about the Optiboot boot loader can be found here:
and here: