I am still trying to figure this out. When powered up, and whenever the reset button is not held down (including when Arduino.exe thinks it’s downloading to the board), the pin-13 LED loops through a pattern with a 3.34-second period. The pattern is a 21-beat pulse train consisting of one long high (1000 ms) and 20 short highs (18-28 ms), separated by lows in a declining sequence: 530 ms, 300 ms, 200 ms, 176 ms, and so on down to 15 ms or so. Does this sound like what one should expect from the baseline contents of the program memory?