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

© 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 Unicode

© 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 Connects all components Allows communication between devices Main board or motherboard 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 Arithmetic and logic unit

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-9 Microprocessor Chips Chip capacities are expressed in word sizes 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

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Specialty Processors Graphics coprocessors Parallel processors Smart cards

© 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 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 billion bytes Gigabyte (GB)1 million 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 Synchronizes operations Expressed in gigahertz Faster clock speed, faster computer What is a gigahertz?

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Expansion Slots and Cards Allow for new devices to be added Open architecture 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 Network interface cards (NIC) TV tuner cards PC cards

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

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved Types of Expansion Buses Industry Standard Architecture (ISA) Peripheral Component Interconnect (PCI) Advanced Graphic Port (AGP) Universal serial bus (USB) FireWire buses HPSB – high performance serial bus Used with digital camcorders & video editing software

© 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.