THE SYSTEM UNIT

THE SYSTEM UNIT

The system unit is a rectangular case that houses the electronic components inside the computer.  The system unit contains the electrical components that make a computer work. Specifically, it contains the following.

●     The power supply

●     The motherboard

●     The CPU

●     Specialized processor chips

●     The system clock

●     RAM chips

●     Expansion slots and boards

●     Bus lines

●     Ports

●      

(a)    Power Supply: The power supply is the component in the system unit that coverts the wall outlet AC into DC power to run the computer.  It can generate a lot of heat; therefore a fan inside the system unit keeps the powers supply (and other components) from getting too hot.

(b)    Motherboard: The motherboard or system board is the main circuit board in the system unit.  The motherboard main circuit inn the system unit, which houses the CPU chip, main memory chips, and expansion slots into which other circuit boards can be inserted for the expansion of the computer system.

Fig:  Motherboard

For a desktop computer, the electronic components and most storage devices such as floppy disk, hard disk and CD ROM drive reside inside the system unit. 

For a laptop computer, the system unit houses almost all of its components including keyboard, pointing devices and monitor.

(c)    Central Processing Unit (CPU): This is the electronic device that interpretes and carries out instructions that tells the computer how to work.  The CPU microchip is the “brain” of the computer.  On a personal computer, the CPU is usually contained on a single chip and is often called a microprocessor. The two principle architects or designs for microprocessor are CISC and RISC.

CISC (Complex instruction set computing) chips that are mostly used in personal computers and conventional mainframes can support large number of instructions, but at relatively low processing speeds.

RISC (Reduced Instruction set computing) chips that are used mostly in workstations eliminate a great many seldom-used instructions, result in working up to 10 times faster than most personal computers.

    Recently copper has replaced aluminum to create the electronic circuitry of CPUs.         - Integrated CPUs

▪      Micro controller

▪      MMX technology.

▪      Parallel processing

▪      Co-processor

▪      Heat sink.

N.B: 

PROCESSING DEVICES:  These process data which is sent to the output devices or stored in secondary memory.  The CPU is the main part(brain) of the computer has two main parts:

(i) Control Unit: directs and coordinates most of the system activities.

(ii) Arithmetic and logic Unit: performs arithmetic and logical functions and

                                            controls the speed of these operations.

(d)   The System clock.  This controls how fast all the operations with in a computer take place or are performed.  Speeds are measured in Megahertz (MHz)

(e)    RAM Chips. These are chips that temporally hold data and instructions that will be needed shortly by the CPU.  These chips are plugged into the motherboard.