マザーボードのバックアップ用のバッテリー

http://www.intel.com/support/motherboards/desktop/d850gb/sb/cs-013231.htm
ここからダウンロードできたテクニカルマニュアル（A2608002.pdf）を見ると

The real-time clock provides a time-of-day clock and a multicentury calendar with alarm features. The real-time clock supports 256 bytes of battery-backed CMOS SRAM in two banks that are reserved for BIOS use.
A coin-cell battery (CR2032) powers the real-time clock and CMOS memory. When the computer is not plugged into a wall socket, the battery has an estimated life of three years. When the computer is plugged in, the standby current from the power supply extends the life of the battery.
The clock is accurate to ± 13 minutes/year at 25 ºC with 3.3 VSB applied.
The time, date, and CMOS values can be specified in the BIOS Setup program. The CMOS values can be returned to their defaults by using the BIOS Setup program.

/  NOTE
If the battery and AC power fail, custom defaults, if previously saved, will be loaded into CMOS RAM at power-on

CR2032ってカシオペアのバッテリーと同じ型ですね。