computing
ESSENTIALS
6
The System Unit
（系统单元）
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computing
ESSENTIALS
Competencies（能力）
System unit types 类型
Coding 编码
major system unit components 主要构成
system boards,microprocessors,memory 主板、处理器、
内存
System clock,expansion slots,boards,bus lines系统时钟、
扩展槽、插板、总线
Ports,cables and power supply 端口、电缆、电源
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ESSENTIALS
System Unit Types（系统单元类型）
• System Unit
• Types of System Units
– Houses electronic
– Desktop
components
– Notebook
– Basic components
•
•
•
•
•
System board
Microprocessor
Memory
Expansion cards
Expansion slots
– Tablet PC
– Personal Digital
Assistant
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Desktop Units（台式机）
• Non-portable 非移动式
• Input/Output devices
located outside the
system cabinet 输入输
出设备位于系统箱外
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Notebook Unit（笔记本）
• Portable
• Monitor attached by
hinges 显示器可开合
• Keyboard and pointing
devices integral to the
system unit 键盘和指示
设备集成于系统单元
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Tablet PC system unit（平板电脑）

Similar to notebook 与笔记本相似

Highly portable 高移动性

Support the use of a stylus or pen
支持记录笔
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PDA Units（掌上电脑）
• Smallest system unit
• All input/output and
secondary storage
devices integral to the
system unit
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ESSENTIALS
Electronic Data & Instructions
（电子数据和指令）
• Binary System
– 0s and 1s
– Each 0 or 1 is a bit
– 8 bits = 1 byte
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Binary Coding Scheme（二进制编码方案）
• American Standard Code for Information
Interchange (ASCII)
• Extended Binary Coded Decimal Interchange
Code (EBCDIC)
• Unicode
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ASCII（美国信息交换标准码）
• Widely used in
microcomputers
• 1 byte = 1 character
• Examples
– Letter R is
represented by 0101
0010
– Number 3 is
represented by 0011
0011
– Character % is
represented by 0010
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EBCDIC（扩充二进制编码的十进制交换码）
• Developed by IBM
• Used in mainframe computers
• 1 byte = 1 character
• Examples
– Letter R is represented by 1101 1001
– Number 3 is represented by 1111 0011
– Character % is represented by 0110 1100
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Unicode（统一字符编码标准）
• Developed by Unicode, Inc. with support from
Apple, IBM, and Microsoft
• Used to support international languages such
as Japanese and Chinese
• 2 bytes = 1 character
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System Board（系统板）
• Connects all components
连接所有部件
• Data path between
devices 设备间的数据通道
• Also called the main board
or motherboard 也叫主板
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System Board Components
（组成）
• Sockets 插孔
Connection points for small specialized electronic parts
小电子部件的连接点
• Chips 芯片
Tiny circuit boards etched into silicon wafer 蚀刻成电路
板后的硅晶片
• Carrier Package芯片封装后的集成电路块
• Slot
connection point for specialized cards or circuit boards
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Microprocessor（微处理器）
• The “brains” of the computer system
• Location of the Central Processing Unit
(CPU)
• Chip capacity expressed in word size
– 16 bit, 32 bit, 64 bit
– Larger the word size
faster the computer
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CPU（中央处理器）
• Control unit
– Directs the movement of electronic signals
between memory and the ALU
• Arithmetic-logic unit (ALU)
– Arithmetic operations
• Fundamental math operations
– Logical operations
• Compares data
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Microprocessors chip（微处理器芯片）
• CISC chip
– Complex Instruction Set Computer
– Intel’s Pentium, Itanium chips,
AMD Athlon, Hammer chips
• RISC chip
– Reduced Instruction Set Computer
– Simpler, cheaper then RISC chips
– Motorola PowerPC chip, DEC
Alpha chip
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Other Microprocessors（其他微处理器）
• Graphics coprocessors
handle 2-D and 3-D graphics images
• Parallel processors
work with one or more other parallel processor chips and
process their respective parts simultaneously
• Smart Cards
– Plastic card that contains a specialized processor chip
– Stores more than 80 times data of conventional magnetic
strip
– Used in credit cards, identification cards, phone cards
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Memory（内存）
• Holding area for data and
instructions
• Three types
– Random-access
memory (RAM)
– Read-only memory
(ROM)
– Complementary metaloxide semiconductor
(CMOS)
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Random-access Memory（随机存储器）
• Holds currently running programs and data
being processed by the CPU
• Volatile storage
– Contained data is lost when computer is
turned off
• Virtual memory
– RAM pages saved to secondary storage
until needed by CPU
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Special RAM Types（特殊RAM类型）
• RAM cache
– Frequently accessed data
– Acts as high-speed, temporary holding
area between CPU and RAM
– Faster processing results
• Flash RAM
– Data is retained even if power
disrupted
– Commonly used in cell phone, digital
cameras
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Read-Only Memory（只读存储器）
• Programs and data are permanently encoded
• CPU can only retrieve data
• Nonvolatile, cannot be changed by the user
• Used for storing special instructions, such as
computer startup
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Complementary Metal-Oxide
Semiconductor（互补金属氧化物半导
体）
• Provides the flexibility and expandability for a
computer system
• Saves data even when computer power is
shut off
• Contents can be changed by the user
• Stores information such as amount of
memory, type of keyboard, mouse
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Memory Measure（内存度量标准）
Unit
Capacity
Kilobyte (KB)
1,000 bytes
Megabyte (MB)
one million bytes
Gigabyte (GB)
one billion bytes
Terabyte (TB)
one trillion bytes
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System Clock（系统时钟）
• Special chip that produces precise
electrical impulses
• Used to coordinate and synchronize
computer operations
• Expressed in megahertz or gigahertz
• Faster clock speed, faster computer
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Expansion Slots（扩展槽）
• Slots provided to add expansion cards to the
system unit
• Used on open architecture system boards
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Expansion Cards（扩展卡）
• Expansion cards used to connect to
devices outside the system unit
• Controller cards, Adapter cards, Interface
cards, plug-in boards
• Usually have ports to connect the card to a
device outside the system unit
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Types of Expansion Cards（扩展
卡类型）
• Network interface cards
(NIC)
• Modem cards
• Sound cards
• Video cards
• SCSI adapter
• TV tuner cards
• PCMCIA cards
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“Plug and Play” （即插即用）
• Hardware and software standards
– Makes system expansion easy for the
user
• Automatically installs drivers and system
configuration
– System unit recognizes the new device
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Bus Lines（总线）
• More lines, the
faster data can
travel
– 64 bit data bus is
faster than a 32 bit
• Data pathways that
link parts of the CPU
together and
components to the
CPU
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Principal Bus Architectures（主要总线
结构）
• Industry Standard Architecture (ISA)
• Peripheral Component Interconnect (PCI)
• Advanced Graphic Port (AGP)
• Universal Serial Bus (USB)
• High performance Serial Bus (HPSB)
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ISA Bus（工业标准结构总线）
• Developed by IBM for personal computers
• Slow
– Originally 8 bit, later expanded to 16 bit
– Still used by some expansion cards
• Replaced by PCI bus in the near future
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ESSENTIALS

PCI Bus（周边元件扩展接口总线）
• Originally developed to meet demands of
graphical user interfaces
• High speed
– 32 bit or 64 bit
• Widely used to connect CPU, memory, and
expansion cards
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AGP Bus（加速图形接口总线）
• Dedicated bus for acceleration of graphics
performance
• Replacing the PCI bus for transfer of video
data
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Other Bus Types（其他总线类型）
• USB（通用串行总线）
– Connects directly to the PCI bus on the
motherboard
– Supports external devices without
inserting expansion cards for each
device
• HPSB（高性能串行总线）
– FireWire
– Similar to USB but faster
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Ports（接口）
• Sockets that connect
external devices to the
system unit
• Four common port
types
– Serial
– Parallel
– USB
– FireWire
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Serial & Parallel Ports（串行和并行接
口）
• Serial Port
– Data sent one bit at a time
– Good long distance transmission of data
• Parallel Port
– Data sent 8 bits simultaneously
– Used for short distances
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USB and HPSB Ports（USB和
HPSB 接口）
• USB Port
– Replacing serial and parallel ports
– Faster
– Each port can support
more than one device
• HPSB Port
– FireWire ports
– Faster then USB ports
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Cables（接线）
• Connect
Input/Output
devices
– Mouse
– Keyboard
– Printer
– Monitor
• Newer cables
– AGP
• graphics monitor
– USB
• joy stick; scanner
– HPSB
• video camera
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Look to the Future（前景）
• Wireless Technology and PDAs
• Personal wearable computer
– POMA®
• Wireless pointing device, head
mounted display
• Developed by Xybernaut
Corporation
• Currently being evaluated for
use in airport security
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