PC Construction and

mittenturkeyElectronics - Devices

Nov 26, 2013 (4 years and 4 months ago)


PC Construction and



Paul Cartwright

Room 7.24 James Parsons

Tel: 231


What is a computer?

Digital computers attributed John Von
Neumann amongst others

Von Neumann model remained unchanged
since 1940s

Von Neumann model is a Logical
representation of digital computers

This model applies to practically all
computers from handheld to mainframe

The System Bus Model

Although modern computers are based on the Von
Neumann model, the model has been streamlined

The system bus model, derived from the von
Neumann model gives an accurate picture of
modern day computer architecture

The system bus model shows schematically how
the components are connected, but nothing about
the physical nature of the components or
interconnecting buses

Physical Components

The CPU (Central Processing Unit) now always
combines the ALU and Control Unit of the von
Neumann model

Very Large Scale Integration (VLSI) has allowed
previously separate systems to exist on a single
silicon chip

The memory system now invariably consists of a
small board onto which is seated several memory

System buses

The system buses are recognisable as tiny
conducting tracks on the motherboard.

Buses can transfer data in parallel. The number of
parallel lines is know as the bus width, and is
specified as a number of bits.

There are several types of buses used for
connecting peripheral devices. A few of these
have become the de
facto industry standard

I/O Devices

I/O devices are very varied in their function,
and there are many different types of buses
to accommodate this

Monitors, keyboards and even hard
are classed as I/O devices

All the features described so far are
common to all widely used types of

Types of computer

There are several different types of computer
widely used. Not all of them are compatible with
each other

Examples are Apple Computers, Intel based
machines (a.k.a IBM PC), SPARC systems, MIPS
based handheld computers

The main criteria for classifying a computer is to
ask “What type of processor does it have?”

Types of processor

The most common processors are divided into two
broad groups CISC
based and RISC

Some new processors borrow technologies from
both groups

Currently, CISC processors dominate the Intel
world, but this is about to change

The latest thing in the world of commercial
processors is the VLIW processor, a RISC
processor that runs CISC code through emulation

From Theory to Practice

For the purposes of this course we will be looking
at IBM PC computers and compatibles

Over 90% of the worlds computers are IBM PC

These computers all employ processors that are
compatible with a dated, but highly proven

The standard is known as the Intel x86 standard

The Desktop PC

First Concepts

Built from commonly available standard

Intel compatible systems are
overwhelmingly popular (a.k.a an IBM PC)

Large scale standardisation of components
causes prices to fall dramatically

PC standards are ‘open’ standards

A view of the PC

The PC system as a whole consists of a base unit,
a monitor, a mouse, a keyboard and possibly some

Most external devices are interchangeable between
different machines

Because of continual improvements and revisions
in wiring and connection standards, some old
hardware may not plug into new PCs and vice

PC Components

Inside the case

At the core of the PC lies the processing

The processing system comprises a
motherboard, central processing unit and

The motherboard is mounted inside a case
to provide shielding and a structure to the

Motherboard and CPU

The motherboard (a.k.a mainboard) is a
large circuit board, providing slots for the
CPU, RAM and Peripheral devices

The CPU is the central component of every
computer system

The CPU contains the logical functions that
execute computer software


All motherboards have a BIOS (Basic input
output system)

The BIOS is a single chip containing
software that control the very low level
functions of the computer

The BIOS is non
volatile. It retains the
software even when the power is switched

Motherboard Slots

All motherboards have slots for peripheral

The three main types of slots in use are PCI,

PCI and ISA slots are general purpose,
although ISA is becoming obsolete

AGP slots are for graphics cards

Peripheral Cards

The most common type of peripheral card is the
video card (a.k.a Graphics Card, Graphics

The video card provides an output to a computer

All PCs must have a video card or equivalent

although some cheaper machines have the video
chipset seated directly on the motherboard instead.

Sound Cards

Another important type of Peripheral card is
the sound card

Sound cards are capable of giving CD
quality sound

Sound cards can be optional, but generally
regarded as essential for most modern PCs

Other types of cards

Other types of peripheral cards include network
cards, TV tuner cards, SCSI cards, internal

There are a wide variety of more specialist cards
that conform to the PCI standard, all of which can
be used in any standard PC

The total number of cards in a single system is
limited by the number of slots on the motherboard,
and possibly by other factors

Case and PSU

The case contains a fan to keep the
computer cool

The case is normally supplied with PSU and
fan in situ

The power supply unit powers the computer
and internal peripheral devices

PSU ratings vary from 230w to 300w

The Base Unit

The whole unit comprising case and its
innards is sometimes called a “base unit”

Often, when a system is upgraded, just the
base unit has to be upgraded

External peripheral devices can be re
at a great saving of cost

Trends in Computer Hardware

Over time, computer hardware becomes obsolete

“Moores law” predicts continual increase in
computing power

Moores Law has held true for forty years and will
almost certainly be valid for the coming decade

There is no such thing as a truly “future proof”

Trends in Computer Hardware

“Feature Size” is a measurement of the
microscopic components inside of a silicon

“Feature size” of CPUs decreases on a
yearly basis

The “chip count” of PC motherboards and
peripheral devices decreases

Trends in Computer Hardware

The “pin count” of computer components
tends to increase

Computers get faster, generate more heat
and consume more power

Software becomes more elaborate and
demanding, requiring hardware upgrade
every 2
5 years