CMOS Memory Map

Traditionally, BIOS settings were stored on a small non-volatile memory chip called CMOS, which was powered by a battery to retain the information in case of a power loss. This battery also powered the RTC (Real-Time Clock) of the motherboard.

This memory is outside of the "regular" memory region of the processor, but it is readable using IN/OUT instructions as shown in CMOS memory map (for Bochs PC emulator)