motherboard

The main, and usually the largest, printed-circuit board of a computer that generally carries the central processing unit (CPU) chip, read only memory (ROM), random access memory (RAM), other major functional elements, and (in PCs) the basic input output system (BIOS). It usually also has sockets into which other circuits boards (called daughter boards), such as for communication ports and peripheral devices, can be plugged in. Main circuit boards of other electronic devices such as telephone systems are referred to also as motherboards. Also called system board.