PC Construction and

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26 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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PC Construction and
Maintenance

week1
-

Introduction

Paul Cartwright

Room 7.24 James Parsons

Tel: 231
-
2108

P.Cartwright@livjm.ac.uk

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
chips

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
-
drives
are classed as I/O devices


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


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
-
based


Some new processors borrow technologies from
both groups


Currently, CISC processors dominate the Intel
-
PC
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
compatibles


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


The standard is known as the Intel x86 standard

The Desktop PC


First Concepts


Built from commonly available standard
components


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
speakers


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
-
versa

PC Components


Inside the case


At the core of the PC lies the processing
system


The processing system comprises a
motherboard, central processing unit and
memory


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

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

BIOS Chip


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
off

Motherboard Slots


All motherboards have slots for peripheral
cards


The three main types of slots in use are PCI,
AGP and ISA


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
Adapter).


The video card provides an output to a computer
monitor


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
modems


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
-
used
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”
computer

Trends in Computer Hardware


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


“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