Computer Hardware

The Processing

Unit

The Computer System

InputDevices

OutputDevices

StorageDevices

CommunicationDevices

Processing Unit

The Processing Unit

• The main part of a microcomputer is called the System Unit

• Most of the processing hardware is on the motherboard

The Processing Unit

• The motherboard is the main circuit board in a computer

A circuit board is a sheet of fiberglass on which electronic components are solderedThese components are connected with traces of copper printed on the surface

The Motherboard

1 – The CPU

2 – The Chipset

3 – Main Memory

4 – The System Bus

5 – The System Clock

FiveMain

MotherboardComponents

The CPU

CPU

Control Unit ALU Registers

The Central Processing Unit has 3 parts

The Control Unit

The Control Unit• Regulates the flow of information• Monitors all operations performed by the

system• Runs Programs:

Fetches program instructions from memory Increments the Program CounterDecodes the instruction Executes the instructionWrites results to memory

The ALU

The Arithmetic and Logic Unit• Performs all calculations (+, - ,*, /)• Returns the result of simple logic

decisions ( is x > y true or false?)• Calculations can be accelerated by a

Floating Point Unit (FPU)

Registers

• Registers• A small amount of high-speed memory on

the CPU• Registers hold the current program

instruction and data • Very fast but also expensive

The Chipset

• A chipset is a group of ICs (Integrated Circuits or computer chips) that are designed to support the CPU.

• On most PC motherboards the chipset has two microprocessors often called the Northbridge and the Southbridge.

The Chipset

The Northbridge chip links the CPU to high-speed components like main memory and video controllers.

The Chipset

The Southbridge chip then links to lower-speed peripheral devices through connections like PCI or PCI-Express.

The Southbridge may also have built-in Ethernet (networking), USB or audio device support

The System Bus

In computers, a bus is a set of connections (wires) that is shared by multiple hardware components in order to communicate.

Bus

A general term for the bus on a motherboard that connects the CPU to all the other components. Also called a local bus.

SystemBus

The System Bus

The main bus between the CPU and main memory typically through the Northbridge.

Frontside

Bus

A common type of local bus that is used to connect the Southbridge chip to peripheral devices such as network expansion cards.

PCIBus

Main Memory-1

CPU

Registers

• Inside the CPU is a small amount of high-speed, expensive computer memory called registers.

• The registers are used for storing data currently being processed in the CPU

Main Memory-2

Main Memory

Ram

CPU

• Most data is stored in Main Memory.• There are two types of Main Memory: RAM &

ROM

Main Memory-3

Main Memory

Ram

Cache

L1

CPU

• Between Main Memory and the CPU is a buffer or temporary storage called cache (pronounced like cash)

• Cache memory stores data so that future requests for that data from the CPU can be served faster.

Main Memory-4

The System Clock

• On the motherboard is a component that generates a clock signal

• This is a timing signal that synchronizes all data transfer in a computer system.

• The CPU also executes instructions at a speed set by the clock signal

The System Clock

• Clock rates are measured in hertz (cycles per second)

• Household AC current alternates at 60 Hertz

German physicist Heinrich Hertzmade important scientific contributions

to the study of electromagnetism.

• 1 megahertz (MHz)= 1 million hertz

• 1 gigahertz (GHz)= 1 billion hertz

The Motherboard

CPU

RAMROM

(BIOS)

Southbridge

ExpansionSlots Northbridge

Ports

A Motherboard