The CPU, storage devices and peripherals each have specialized roles in the security archecture. The CPU, or microprocessor, is the brains behind a computer system and performs calculations as it solves problemes and performs system tasks. Storage devices provide both long-and short-term stoarge of information that the CPU has either processed or may process. Peripherals (scanners, printers, modems, etc) are devices that either input datra or receive the data output by the CPU.
The motherboard is the main circuit board of a microcomputer and contains the connectors for attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices.
Reference(s) used for this question: TIPTON, Harold F., The Official (ISC)2 Guide to the CISSP CBK (2007), page 308.