PC Construction and Maintenance week1 - Introduction Paul Cartwright Room 7.24 James Parsons Tel:

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