66 CHAPTER THE SYSTEM UNIT

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-2 Competencies Describe the four basic types of system units Discuss how a computer uses binary codes Describe the major system unit components Describe system boards, microprocessors, and memory Describe the function of the system clock, expansion slots, boards, and bus lines Discuss ports, cables, and power supply

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-3 System Units Microcomputers Desktop Notebook Tablet PC Handheld

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-4 Electronic Data and Instructions Data and instructions are represented electronically Computers recognize digital signals Binary system Bit Byte What is the difference between digital and analog

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-5 Binary Coding Scheme Two state system Off/on electrical states Characters represented by 0s and 1s Three types of schemes ASCII - American Standard Code for Information Exchange EBCDIC - Extended Binary Coded Decimal Interchange Code( used for large computers) Unicode ( for international languages like Chinese and Japanese.

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-6 Binary Code CodeUses ASCIIMicrocomputers EBCDICLarge Computers UnicodeInternational Languages

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-7 System Board Main board or motherboard Connects all components Allows communication between devices Circuit board electronic components Sockets Slots Bus lines

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-8 Microprocessor Central Processing Unit (CPU ) - Two basic components Control unit  Tell the rest of the computer how to carry out a program’s instructions  It directs the movement of electronic signals between memory, instructions and arithmetic logic unit.  Direct control signals between the CPU and I/O devices. Arithmetic and logic unit (ALU) Perform two types of operations Arithmetic and logic

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-9

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. Quiz 3 Special Quiz 6-10

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Microprocessor Chips Chip capacities are expressed in word sizes A word is the number of bits that can be accessed at one time by the CPU. Types of microprocessor chips CISC chips: Complex instruction chips Most widely used design Used by Intel RISC chips: Reduced instruction set computer chips Uses fewer instructions Design is simpler and less costly Used by the PowerPC ( is a RISC chip produced by Motorola)

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Power PC CISC CPU

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Specialty Processors Graphics coprocessors (for displaying and manipulating 2-D and 3-D graphics) Parallel processors - To run or process large programs - Break the program into parts and assign the parts to separate processor Smart cards (master card)

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Memory Holding area for data, instructions, and information Types of memory chips RAM – holds programs and data - Virtual Memory ROM – fixed start-up instructions CMOS – flexible start-up instructions

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Memory Capacity UnitCapacity Megabyte (MB)1 million bytes Gigabyte (GB)1 billion bytes Terabyte (TB)1 trillion bytes

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved System Clock Important measurement indicating speed Located on a small chip Produces electrical beats(impulse) Synchronizes operations Expressed in gigahertz Faster clock speed, faster computer the clock speed determines how many instructions per second the processor can executeprocessor execute

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Expansion Slots and Cards Allow for new devices to be added Open architecture( allow user to expand their systems by providing slots on the system board) Slots provide for expansion Expansion cards are also called … Plug-in boards Controller cards Adapter cards Interface cards

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Commonly Used Expansion Cards Video cards Modem cards (internal modem) Network interface cards (NIC) TV tuner cards PC cards (PCMCIA) Users are able to add memory, wired and wireless communications, multimedia and security features by inserting ExpressCard modules into compliant systems Plug and play

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Bus Lines Connect parts of the CPU to each other Connect the CPU to other devices on the system board. Data roadway for traveling bits Measured as bus width More lanes, faster traffic Two basic categories of Expansion BUSES System buses ( connect CPU to Memory) Expansion buses ( connect CPU to slots on the system board)

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Types of Expansion Buses Industry Standard Architecture (ISA) ( 8 or 16 bus width ) Peripheral Component Interconnect (PCI) (32 or 64 bus width) Advanced Graphic Port (AGP) (transferring video data) Universal serial bus (USB) To support several external devices without using expansion cards or slot FireWire buses HPSB – high performance serial bus Used with digital camcorders & video editing software

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved PCI ISA AGP USB FireWire

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Ports Socket for connecting external devices Four common ports Serial Parallel USB FireWire

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Power Supply Computers require direct current (DC) DC power provided by converting alternating current (AC) from wall outlets or batteries Desktop computers use power supply units Notebooks and handhelds use AC adapters AC adapter Power Supply Unit

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved A Look to the Future Xybernaut Corporation Wearable computers Called POMA Includes… Windows CE Wireless pointing device Head-mounted display MP3 player Abridged Windows Office programs

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Key Terms AC adapter (164) accelerated graphics port (AGP) (163) adapter card (159) alternating current (AC) (164) analog (151) arithmetic operation (155) Arithmetic logic unit (AL ASII (152) binary coding scheme (152) binary system (151) bit (151) bus (162) bus line (154) bus width (162) byte (151)

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Key Terms video card (159) video capture card (159) video recorder card (159) volatile storage (157) virtual memory (157) word (155) workstation (155)

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved FAQs What are the four basic types of system units? What is analog? What is digital? What is a microprocessor and what does it do? What is RAM? What is ROM? I hear a lot about flash memory. What is it? I need a USB port to install a wireless mouse. What are ports? What is a network card?

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Discussion Questions Explain how a computer understands instructions. Define memory and describe three types of memory chips. Explain the purpose of expansion cards and slots. Give examples of some commonly used expansion cards. Describe how bus lines work.