What is the 4prong black port next the the IR plug?

ok so I pointed at it with the red arrow on one of the pics. I'm just wondering what that is. Is this a usb port? or a power slot? I cant seem to find ANYTHING on this thing. I found an internal bluetooth mod that went into the same slot but i'm afraid to try it. I also looked at schematics for this apple tv and nothing. Anyone have any good guesses?

maybe I can use it for a sata drive?