- also ATmega1284P and ATmega644A mentioned in the article doesn't support external code memory nor changing the code memory after boot. However they do support

- also ATmega1284P and ATmega644A mentioned in the article doesn't support external code memory nor changing the code memory after boot. However they do support a boot loader that can load code initially. So you would have to implement some sort of paging by resetting the cpu to give control to the bootloader to load the new code. Sound like fun. Also the kernel itself is far too large to fit in code memory, so it would constantly have to page parts in and out through this mechanism.