Does anyone know what SW2G1 is on the mainboard? i’m in the middle of fixing a RROD and i noticed something rattling around in it. 
Device SW2G1 is a ball bearing switch. Probing with a voltmeter while changing the orientation of the board reveals that the impedance of the switch changes depending upon orientation. The ball bearing in this switch lends the Xbox360 motherboard a distinctive rattle when shaken.
Presumably, the orientation switch is required because the Xbox360 can operate in vertical or horizontal orientations and certain UI parameters must be adjusted accordingly (such as the wireless controller indicator lights).