1. Chapter 5
The System Unit

2. Overview Discuss the Types of System Units Describe System Boards
Discuss Processors
Discuss Memory
Discuss Expansion Slots and Cards
Bus Lines, Bus Widths, Expansion Buses
Describe Ports
Discuss Power Supplies
Discuss Numbers and Characters

3. System Unit Types Desktops Notebooks Tablets Handhelds Tower Unit
All-in-one
Notebooks
Laptops
Netbooks
Tablets
Handhelds
System unit (key term) is also referred to as the system chassis(Key Term)
All computers have a system unit
Desktop (key term) – contains electronic components and selected secondary storage.
System units are placed in tower units (key term) or tower computers (key term)
Notebook (key term) – contains electronic components, secondary devices, and input devices – often called laptop computers (Key Term)
Netbook (key term) – like notebooks, but less powerful and less expensive, used for web browsing and
Tablet (Key Term) or tablet computer – flat screen and typically do not have a keyboard.
Operating system controls their operations
Hand-held computer systems (key term) – entire computer system is contained in the device. Smartphone (key term) is the most popular

4. System Board AKA Motherboard All Components Connect to It
All External Devices Connect to It
Acts as Data Path and Traffic Monitor
Provides Sockets
Connection Point For Chips
System board (key term) or mainboard (key term) or motherboard (key term) – controls communication for the entire computer system

5. System Board Components
Chips
AKA Semiconductor, Integrated Circuit
Tiny Circuit Boards on Silicon Squares
Mounted on Carrier Packages
Slots
Connection Points for Circuit Boards
Provide Expansion Capability
Bus Lines
Communication Pathways for Components
Sockets (key term) – connection point for chips
Chips (key term) contain numerous circuits etched on a small wafer of layers of silicon and other materials
Chips are mounted on carrier packages (Key Term)
Chips are also referred to as a silicon chip (Key Term), semiconductor (Key Term), or integrated circuit (Key Term)

6. Microprocessor AKA Central Processing Unit or Processor Components
Brain of the Computer System
Components
Control Unit
Directs Movement of Electronic Signals
Between Memory, ALU, Input and Output Devices
Arithmetic-logic Unit (ALU)
Arithmetic and Logical Operations
Central Processing Unit (CPU) (key term) or processor is located on the microprocessor (key term) chip and has two components - the control unit and the arithmetic-logic unit
Control Unit (key term)
Program instructions
Directs flow between memory and Arithmetic-Logic Unit
Directs flow between CPU and I/O devices
Arithmetic-Logic Unit – ALU (key term)
Two types of operations
Arithmetic operation (Key Term)
Logical operation (Key Term)

7. Microprocessor Chips Chip Capacities Expressed in Word Size Word
Number of Bits Processed at a Time
64-bit Word Standard
Clock Speed
Processing Speed
Times Per Second CPU Processes Data
A word (Key Term) is the number of bits that can be accessed at one time by the CPU
32 bit word computer can access 4 bytes at a time
64 bit word computer can access 8 bytes at a time
Clock speed (key term) – number of times the CPU can fetch and process data and instructions in millionths of a second, or microseconds

8. Microprocessor Chips System Clock
Processor Speed Measured by Ticks/Second
MHz – One Million Ticks/Second
Type 100 Words/Minute = 8 Characters/Second
MHz
Character ► 50,000 Other Tasks ► Character
GHz – One Billion Ticks per Second

9. Microprocessor Chips Multi-Core Chip Coprocessors
Multiple Separate and Independent CPUs
Parallel Processing
Divide Tasks that can be Distributed Across Each Core
Supported by Windows 8 and Mac OS X
Coprocessors
Used to Improve Specific Operations
e.g., Graphics Processing Unit (GPU)
Multicore chip (key term) – allow a single computer to run two or more operations at the same time
Example: A dual-core process could have one core computing a complex Excel spreadsheet while the other is running a multimedia presentation.
Parallel Processing (key term) – dividing tasks into parts that can be distributed across each core

10. Memory Holding Area RAM (Random-access Memory)
For Data, Instructions, and Information
RAM (Random-access Memory)
Volatile
Holds Program Instructions and Data
That CPU is Presently Processing

11. Memory
Sizes

12. Memory Cache Memory ROM (Read-only Memory) Flash Memory
Temporary High-speed Holding Area
Between Memory and CPU
Stores Most Frequently Used Data
ROM (Read-only Memory)
Non-volatile, Cannot be Updated
Flash Memory
Non-volatile, Can be Updated

13. Expansion Slots and Cards
Allow for System Expansion
Graphics Cards
Sound Cards
Network Interface Cards (NIC)
Wireless Network Cards
Plug and Play
ExpressCard
Expansion slots (key term) used to insert expansion cards (key term)
Graphics cards (Key term) - connect the system board to the monitor; convert internal electronic signals to video signals
Sound cards (key term) – convert electronic signals to audio signals and accept audio input from microphones
Network Interface Cards (Key Term) (NICs or Network Interface Cards) - connect system unit to a cable (Key Term) attached to a network
Wireless network cards (key term) – allow computers to be connected without cables
Plug and Play (key term) – plug in any device and have it work immediately
PC cards (key term) – plug into PCMCIA slots (key term) or PC cards slots (key terms) on notebooks, tablets or handhelds. Also known as ExpressCard (key term) slots

14. Bus Lines Pathway for Bits Bus Width Categories
Travel to/from CPU and Components
Bus Width
Number of Bits that Can Travel at Once
Categories
System Bus
Expansion Bus
Bus lines provide (key term) data pathways that connect various system components
A bus line is also called a bus (Key Term)
Bus width (key term) is the number of bits that can travel at once
It is a pathway for bits representing data and instructions
A bus is similar to a multilane highway.
Every computer has two basic categories of buses
System bus (key term) – connects the CPU to memory on the system board
Expansion bus (key term) – connects the CPU other components and to slots on the system board

15. Ports Sockets for External Devices Standard Ports Cables
Connects to System Board or Cards
Standard Ports
VGA, USB, Firewire, Ethernet
Cables

16. Power Supply Convert AC to DC Power System Unit Components AC Adapters
Notebooks and Handhelds
Can Recharge Batteries
Direct current (DC) powers computers
Desktop computers have a power supply (key term) unit located within the system unit
Notebook computers use AC adapters (key term) that are located outside the system unit
Netbook and handheld use AC adapters

17. Electronic Data and Instructions
Analog Signals
Represent Different Tones, Pitches, Volume
Digital Electronic Signals
Represent Two Discrete States
On / Off
Recognized By Computers
Binary is the Equivalent Numbering System
Digital signals (key terms) – electronic signals only recognized by computers
Analog signals (key terms) – created by voice

18. Numeric Representation
Binary System
Bit (Binary Digit)
2 Possible Digits
On = 1; Positive Charge
Off = 0; No Charge
Byte
Eight Bits Grouped Together
Represent Letters, Numbers, Punctuation
Hexadecimal System
16 Possible Digits
Binary System (key term) – consists of only two digits, 0 and 1. Each 0 or 1 is called a bit (key term) which is short for binary digit
8 bits grouped together is a byte (key term)
Binary numbers are difficult to read so they are represented in a hexadecimal system (key term) or hex using 16 digits to represent binary numbers 3 5 D

19. Character Encoding ASCII EBCDIC Unicode
American Standard Code for Information Interchange
Microcomputers
EBCDIC
Extended Binary Coded Decimal Interchange Code
Mainframe
Unicode
Uses 16 bits
Character encoding standards (key term) assign a unique sequence of bits to each character
Historically used ASCII (key term) for microcomputers and EBCDIC (Extended Binary coded Decimal Interchange Code) (key term) for mainframes
Unicode (key term) is a new character encoding using 16 bits

20. Careers in IT Computer Technicians
Repair and Install Components and Systems
Work On PCs, Mainframes, Networks, Printers
Associate Degree or Computer Repair Cert
Annual Salary of $31,000 - $46,000
Character encoding standards (key term) assign a unique sequence of bits to each character
Historically used ASCII (key term) for microcomputers and EBCDIC (Extended Binary coded Decimal Interchange Code) (key term) for mainframes
Unicode (key term) is a new character encoding using 16 bits