Not really sure if this is AVR, General Electronics or Off Topic...
There have been more posts than I can count here on AVR Freaks that recommend caps for and close to each power pin.
So why do the Arduinos generally ingnore this?
Not counting the caps associated with the power regulator, we see:
- Arduino Uno - 1 cap for ATmega328P and 1 for ATmega16U2
- Arduino Pro Mini - 1 cap for the three power pins
- Arduino Micro - 2 caps for 4 power pins on the ATmega32U4
- Arduino mega2560 - 3 caps for the ATmega2560 and 1 for ATmega16U2
The following do follow the cap per power pin guideline:
- Arduino Gemma
- Arduino Zero