The E4809-045-167-C is a high-grade CMOS memory card by Okuma, prevalent in computer systems and motherboards for maintaining BIOS settings. It's traditionally referred to as CMOS RAM due to its use of volatile, low-power CMOS SRAM and has a typical capacity of 256 bytes. The memory card is supplied by a CMOS battery when the system and standby power are disconnected. The real-time clock and CMOS RAM are now unified into one component in newer motherboards. The non-rechargeable memory battery, usually a lithium coin cell, has an estimated life span of three years, though lifespan can be shortened by high temperatures or protracted power-off periods. Changing the battery may result in the system time settings and CMOS BIOS reverting to their default configurations, although this can be avoided by replacing the battery while the board is connected to an electrical socket. Most boards also provide a four-pin header to enable external 3.6v battery connection.
