Wow...took me a while to find that. It is where a button battery carrier would go if the board included one. My guess is they reserved a spot for it but eventually wacked it in a cost-cutting decision. The board doesn't keep the time because it has no battery attached. Instead it synchronizes time with the Internet when it boots. Seems like a reasonable cost cutter.i wonder what the BATT_CON is for on the board
My big mystery is the three-pin jumper block labeled SW1. There can't be any BIOS reset so what else could it change? There is also the white four-pin floppy-drive looking connector over by the DC IN connectors. Power out? For what purpose?