The "9V" pin is connected to the cathode of the power input protection diode. So it's not exactly the same as connecting to the power jack, but you can use it to feed unregulated power to the 5V regulator input.
The "9V" pin is connected to the cathode of the power input protection diode. So it's not exactly the same as connecting to the power jack, but you can use it to feed unregulated power to the 5V regulator input.