When I read about registers I always encounter the following illustration:
So there are 32 registers in the above diagram. They are processor registers.
But in the data-sheet of ATmega328P at page 428 there is a section called "Register Summary".
Here in that list there are much more than 32 registers. Do the rest of the registers physically stay somewhere else?
Lest's take an example of ADMUX register. Where is that register physically inside the DIP? It is not one of the 32 registers? And if stays somewhere else how does it connected to the ALU?