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Chapter 4 The Components of the System Unit

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1 Chapter 4 The Components of the System Unit

2 Instruction Data Information Instructions Data Information
Ch 4 System Unit Ch 1 – Introduction Ch 2 – Internet & WWW Ch 3 – Application Software Ch 8 – System Software Ports Cards Buses Clock Power Drives Control Unit Arithmetic Logic Unit (ALU) Instruction Data Information Memory Input Devices Ch 5 Output Devices Ch 6 Information Data Instructions Data Information Storage Devices Ch 7

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?
Processor Memory Clock Adapter (extension) cards Sound card Video card Drive bays Power supply Ports Buses

6 Processor The 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 Memory Processor Step 1. Fetch Obtain program instruction from memory
Control Unit Memory Step 1. Fetch Obtain program instruction from memory Step 4. Store Write result to memory Step 2. Decode Translate instruction into commands ALU Step 3. Execute Carry out command

10 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

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

13 How speed of the processor is measured?
Each tick is a clock cycle Pace of system clock is clock speed Clock speeds are in the gigahertz (GHz- billion ticks per sec) Processor speed is also measured in millions of instructions per second (MIPS)

14 Instructions per 1 watt energy (in millions) (MIPW)
Clock speed (GHz) Instructions per sec (MIPS) Instructions per 1 watt energy (in millions) (MIPW)

15 What is pipelining? CPU begins executing the second instruction before completing the first instruction Machine Cycle (without pipelining) Machine Cycle (with pipelining) Instruction 1 Instruction 2 Instruction 3 Instruction 4

16 Doing Laundry Ann, Brian, Cathy, Dave each have one
load of clothes to wash, dry, fold, slash A B C D Washer takes 30 minutes Dryer takes 30 minutes Folder takes 30 minutes Stasher takes 30 minutes

17 Sequential Laundry Sequential laundry takes 8 hours for 4 loads 30
Time 6 PM 7 8 9 10 11 12 1 2 AM T a s k O r d e B C D A Sequential laundry takes 8 hours for 4 loads

18 Pipelined laundry takes 3.5 hours for 4 loads
12 2 AM 6 PM 7 8 9 10 11 1 Time 30 T a s k O r d e B C D A Pipelined laundry takes 3.5 hours for 4 loads

19 What is parallel processing?
Using multiple processors simultaneously to execute a program faster Requires special software to divide problem and bring results together Control Processor Processor 1 Memory Processor 2 Memory Processor 3 Memory Processor 4 Memory Results combined

20 Single-core processor
Multi-core processor One processor on a chip More then one processor on a chip

21 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

23 What is a bit?

24 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 carries numeric value of = 85

27 Coding systems to represent text data
ASCII—American Standard Code for Information Interchange Unicode—coding scheme capable of representing all world’s languages


29 Memory

30 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? The operating system and other system software Application programs Data being processed and the resulting information


32 Memory consists of locations (bytes)
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 Nonvolatile memory Volatile memory
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

34 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 slot Adapter card holds an adapter card enhances
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


46 What are USB ports? USB (universal serial bus) port can connect up to 127 different peripherals together with a single connector type PCs typically have several USB ports Single USB port can be used to attach multiple peripherals Third USB device connects to second USB, and so on Second USB device connects to first USB First USB device connects to USB port USB 2.0

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

48 Firewire port SCSI port eSATA port IrDA port Serial port MIDI port
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?
Allow users to attach specialized peripherals or transmit data to wireless devices MIDI (Musical Instrument Digital Interface) port IrDA (Infrared Data Association) port Bluetooth port


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
Converts AC Power into DC Power Fan keeps system unit components cool

57 To see the online addition to the book click here

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