Discovering Computers

Chapter 4The Components of the

System Unit

2

Ch 4System Unit

Arithmetic Logic Unit

(ALU)

InputDevices

Ch 5

StorageDevices

Ch 7

OutputDevices

Ch 6

MemoryData Information

InstructionsData

Information

InstructionData

Information

Control Unit

Ch 1 – Introduction

Ch 2 – Internet & WWW

Ch 3 – Application Software

Ch 8 – System Software

PortsCardsBusesClockPowerDrives

3

What is the system unit?

Case that contains electronic components of the computer used to process data

4

What is the motherboard?

Main circuit board of the system unit

Also called system board

5

Components inside the system unit?

Memory Clock Adapter

(extension) cards Sound card Video card

Drive bays Power supply Ports Buses

Processor

6

ProcessorThe processor, also called the central

processing unit (CPU), interprets and carries out the basic instructions that operate a computer

Contains a control unit and an arithmetic logic unit (ALU)

7

Control unit is the component of the processor that directs and coordinates most of the operations in the computer

Arithmetic logic unit (ALU) performs arithmetic, comparison, and other operations

8

For every instruction, a processor repeats a set of four basic operations,

which comprise a machine cycle

9

Processor

Control Unit

Memory

Step 1. Fetch Obtain program instruction from memory

Step 2. Decode Translate instruction into commands

Step 4. Store Write result to memory

Step 3. Execute Carry out command

ALU

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The processor contains registers, that hold data and instructions

The processor contains circuits that perform instructions using data

11

The system clock controls the timing of all computer operations

System Clock

Generates regular electronic pulses, or ticks, that set operating pace of components of system unit

13

Each tick is a

clock cycle

Pace of system clock is clock speedClock speeds are

in the gigahertz (GHz- billion ticks per sec)

Processor speed is also measured in

millions of instructions per second (MIPS)

How speed of the processor is measured?

14

Clock speed (GHz) Instructions per sec (MIPS)

Instructions per 1 watt energy (in millions)

(MIPW)

15

What is pipelining?

Machine Cycle (without pipelining)

Machine Cycle (with pipelining)

Instruction 1

Instruction 2

Instruction 3

Instruction 4

CPU begins executing the second instruction before completing the first instruction

16

Doing LaundryAnn, Brian, Cathy, Dave each have one

load of clothes to wash, dry, fold, slash A B C D

°Dryer takes 30 minutes

°Folder takes 30 minutes

°Stasher takes 30 minutes

°Washer takes 30 minutes

17

Sequential Laundry

Sequential laundry takes 8 hours for 4 loads

Task

Order

B

C

D

A

30Time

3030 3030 30 3030 3030 3030 3030 3030

6 PM 7 8 9 10 11 12 1 2 AM

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Pipelined Laundry

Pipelined laundry takes 3.5 hours for 4 loads

Task

Order

B

C

D

A

12 2 AM6 PM 7 8 9 10 11 1

Time303030 3030 3030

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What is parallel processing?

Control Processor

Processor 1

Memory

Processor 2

Memory

Processor 3

Memory

Processor 4

Memory

Results combined

Using multiple processors simultaneously to execute a program faster

Requires special software to divide problem and bring results together

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Single-core processor

Multi-core processor

One processor on a chip

More then one processor on a chip

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Data of various nature are

presented inside a computer in a

digital form. We will see how.

22

Analog signals are continuous and vary in strength and quality

Digital signals are in one of two states: on or off

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What is a bit?

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Eight bits grouped together as a unit are called a byte.

Each byte has a unique address.

Each of eight bits in a byte has a position

25

What a byte contains vs. what an output device will convey?

Contains: A sequence of 8 binary digits

Means: Number Character Instruction Sound pitch Color … Depending on device

26

Representing numbers Numbers have the most natural

presentation. Each bit of a byte has a value depending on the position of the bit in a byte.

For example byte 01010101 carries numeric value of 64+16+4+1 = 85

27

Coding systems to represent text data

ASCII—American Standard Code for Information Interchange

Unicode—coding scheme capable of representing allworld’s languages

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Memory

Memory consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions, and the results of processing the data

What has to be stored?

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The operating system and other system software

Application programs

Data being processed and the

resulting information

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Memory consists of locations (bytes). Each location in memory has an address

The number of locations in memory is memory size.

It is measured in kilobytes (KB or K), megabytes (MB), gigabytes (GB), or terabytes (TB)

33

The system unit contains two types of memory:

Volatile memory

Loses its contents when power is

turned off

Example: RAM

Nonvolatile memory

Does not lose contents when

power is removed

Examples: ROM, flash memory

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Read-only memory (ROM) refers to memory chips storing permanent data and instructions

35

Adapter (Extension) Cards A flash memory card allows

users to transfer data from mobile devices to desktop computers

An PC card adds various capabilities to computers

36

Flash memory can be electronically rewritten

37

Flash memory includes: Memory cards, USB flash drives, and PC Cards modules

38

Memory cache speeds the processes of the computer because it is faster than memory and stores repeatedly used information

39

Access time is the amount of time it takes the processor to read from memory. Measured in nanoseconds

40

Expansion slotholds an

adapter card

Adapter cardenhances

functions and

provides

connections to

peripherals

41

With Plug and Play, the computer automatically configures adapter cards and peripherals as you install them

42

Ports and Connectors

A port is the point at which a peripheral attaches to or communicates with a system unit (sometimes referred to as a jack)

A connector joins a cable to a port

43

Port connects external devices to system unit

44

On a notebook computer, the ports are on the back, front, and/or sides

45

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Third USB device connects to second USB,

and so on

Third USB device connects to second USB,

and so on

Second USB device connects

to first USB

Second USB device connects

to first USBFirst USB device connects

to USB port

First USB device connects

to USB port

Single USB port can be used to attach

multiple peripherals

Single USB port can be used to attach

multiple peripherals

PCs typically have several USB ports

PCs typically have several USB ports

What are USB ports?

USB (universal serial bus) port can connect up to 127 different peripherals together

with a single connector type

USB (universal serial bus) port can connect up to 127 different peripherals together

with a single connector type

USB 2.0

47

You can attach multiple peripherals using a single USB port with a USB hub

48

Other types of ports include:

Firewire port

Bluetooth port

SCSI port

eSATA port

IrDA port

Serial port

MIDI port

49

What are special-purpose ports?

MIDI (Musical Instrument Digital Interface) port IrDA (Infrared Data Association) port Bluetooth port

Allow users to attach specialized peripherals or transmit data to wireless devices

50

51

A Bluetooth wireless port adapter converts a USB port into a Bluetooth port

A smart phone might communicate with a notebook computer using an IrDA port

52

What is a serial port?

Transmits one bit of data at a time

Connects slow-speed devices, such as mouse, keyboard, modem

53

What is a parallel port?

Connects devices that can transfer more than one bit at a time, such as a printer

54

Buses

What is a bus? Channel that allows devices

inside computer to communicate with each other

Bus width determines number of bits transmitted at one time

55

Bays

What is a bay? Opening inside system

unit used to install additional equipment

Drive bays typically hold disk drives

56

Power Supply and cooling

ConvertsAC Power

intoDC Power

Fan keepssystem unit

components cool

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