Optiboot confusion

I have a new Uno, and wish to use the MCUSR register to determine whether a restart was due to a power-up or a reset button press.

I gather that I need to install Optiboot, but this is where it gets confusing. There's lots of history, and it's not clear what is required with a brand-new Uno and Arduino 1.8.9.

  1. Is it required to burn Optiboot onto the Arduino ?

  2. If not, is installing Optiboot 8.0 using the Boards Manager sufficient ?

If have NOT done 1), but have done 2). Still MCUSR shows as 0 whether on power-up or on reset button press.

Thanks !

  1. Optiboot is on every normal Uno. Although I don't know which version.

  2. Just installing it and not burning it will not change a thing :wink:

I wrote this guide some time ago:
https://tttapa.github.io/Pages/Arduino/Bootloaders/ATmega328P-custom-frequency.html

Pieter

You need to burn the new version of optiboot to the arduino to get the new features (IIRC the MCUSR thing was pretty recent, and is almost certainly not in the bootloader on the official boards)