1. Chapter 2

2. What is the system unit?
A boxlike case that houses the computer’s main hardware components

3. What are the different types of system units?
Notebook
Desktops
Personal Digital Assistant

4. Inside the System Unit

5. What’s inside the system unit?
Motherboard (mainboard)- Large printed circuit board with thousands of electrical circuits
Power supply- Transforms alternating current (AC) from wall outlets to direct current (DC) needed by the computer
Cooling fan- Keeps the system unit cool
Internal Speaker- Used for beeps when error is encountered
Drive bays- Housing for the computer’s hard drive, floppy drive and CD-ROM / DVD-ROM drives
Click N Learn

6. What’s on the motherboard?
System clock- Synchronizes the computer’s internal activities
Microprocessor (CPU)- Central processing unit interprets and carries out instructions given by software
Memory- Enables the computer to retain information
Chipset- A collection of chips that provide the switching circuitry needed to move data
Input/Output buses- Pathways that allow the microprocessor to communicate with input and output devices
Click N Learn

7. The Motherboard Microprocessor Keyboard / Mouse Ports Memory Slots
Printer Port
Video Port
AGP Slot
PCI Slots
Chipset

8. Microprocessor (CPU)

9. What are the types of CPUs?
Intel
Advanced Micro Devices (AMD)
Pentium IV
Pentium III
Pentium MMX
Cyrix
Motorola (Apple)

10. What are the components of the CPU?
Control unit- Coordinates and controls all parts of the computer system
Arithmetic-Logic unit- Performs arithmetic or logical operations
Registers- Stores the most frequently used instructions and data
Click N Learn

11. How do CPUs work?
Control Unit- Manages four basic operations (machine cycle)
Fetch- Gets next program instruction from the computer’s memory
Decode- Figure out what the program is telling the computer to do
Execute- Perform the requested action
Write-back (Store)- Write (store) the results to a register or to memory
Arithmetic-Logic Unit (ALU)- Perform basic arithmetic or logic operations
Add, Subtract, Multiply, Divide
Compare two items to see which one is larger or smaller
Intel

12. How a CPU works Click to animate. Click one time only Control unit ALU
DECODE
EXECUTE
Memory
FETCH
STORE

13. What determines a CPUs performance?
Data bus width- The number of pathways within the CPU that transfers data (8, 16, 32, 64)
Word size- The maximum number of bits of data that the CPU can process at a time (8 bits, 16 bits, 32 bits, 64 bits)
Operations per cycle (clock speed)- The number of clock cycles per second measured in Megahertz (MHz) or Gigahertz (GHz)
Specifications:
Clock Speed: 1.0 GHz
System / Front Side Bus Speed: 133 MHz
Level 1 Cache: 16K Instruction + 16K data
Level 2 Cache: 256 KB

14. Memory

15. What is memory?
A term for a device that enables the computer to retain (store) information.

16. What are the types of memory?
Volatile memory (Random Access Memory/RAM; Cache Memory; Virtual Memory)- Contents of memory are erased when power supply is turned off. Also called Temporary storage.
Nonvolatile memory (Read Only Memory/ROM; Flash Memory)- Contents of memory are not erased when power is turned off. Also called Permanent storage.

17. What is Random Access Memory / RAM?
A type of volatile memory that stores information temporarily so that it’s available to the CPU.

18. What are the different types of RAM?
Dynamic RAM- A memory chip that needs to be refreshed periodically or it loses its data
Synchronous DRAM (SDRAM)- Synchronized with the computer’s system clock
Rambus DRAM (RDRAM)- Uses fast bus to send and receive data within one clock cycle. Faster than SDRAM
Double Data Rate SDRAM (DDR SDRAM)- A type of SDRAM that can send and receive data within one clock cycle.
Kingston

19. What is a memory module?
A narrow printed circuit board that holds memory chips
Three types
Single Inline Memory Module (SIMM)- 30 or 72 pin connectors. Available in 1MB, 4MB, 16MB, and 32MB versions
Dual Inline Memory Module (DIMM)- 168 or 184 pin connectors. Available in 8MB, 16MB, 32MB, 64MB, 128MB, 256MB, and 512MB versions
Rambus Inline Memory Module (RIMM)
Kingston

20. DIMM
RIMM
NOTEBOOK DIMM
SIMM

21. HOW DOES RAM WORK?
CHIPS CONTAIN MEMORY LOCATIONS CALLED MEMORY ADDRESSES
THE CPU STORES AND RETRIEVES DATA BY GOING TO THE MEMORY ADDRESSES
Intel

22. HOW RAM WORKS
CLICK TO BEGIN ANIMATION
MONITOR
WEB
RAM
KEYBOARD
CPU

23. What is cache memory?
Primary cache (Level 1 or L1)- Located within the CPU chip, it is the memory the microprocessor uses to store frequently used instructions and data.
Secondary cache (Level 2 or L2; Backside Cache)- Located near the CPU, it is the memory between the CPU and RAM
Faster than RAM

24. FULL What is virtual memory? Part of the hard disk is reserved as RAM
When RAM modules become full the CPU accesses the hard disk to store and retrieve data
Slower than RAM
FULL

25. Buses

26. What is a chipset? A collection of chips that work together
Provides circuitry to move data to and from the rest of the computer

27. What are input/output (I/O) buses?
Pathways that enable the CPU to communicate with input/output devices
Typically the buses contain slots called expansion slots, in which expansion cards are inserted
Expansion slots
Expansion card

28. What are the types of I/O buses?
Industry Standard Architecture (ISA)- Slowest type of bus
Personal Computer Interface (PCI)- Faster than ISA; supports plug and play
Accelerated Graphics Port (AGP)- Designed for video adapters
Universal Serial Bus (USB)- Allows up to 127 devices to be connected to the computer at one time; supports plug and play

29. Outside the System Unit

30. What’s on the outside of the system unit?
Power switch- Located on the back; turns power on/off to the computer
Receptacles- Called connectors or ports; Usually located on the back; Used to plug in peripheral devices, keyboard, mouse and monitor
Front panel- Contains drive bays, various buttons and lights
BACK
FRONT
Drive bays
On/off switch
Reset button
Indicator lights

31. What types of ports do computers have?
Serial port- Data flows in a series of pulses, one after another one bit at a time; Slow data transfer rate; Modems
Parallel port- Data flows through eight wires allowing the transfer of eight bits of data simultaneously; Faster than serial port; Printers
PS/2 port (mouse port)- Special serial port to connect mouse
Small Computer System Interface (SCSI)- Found mostly on MacIntosh computers; A parallel port allowing up to eight devices to be connected at a time
Universal Serial Bus (USB)- Allows up to 127 devices to be connected at a time
1394 port (Firewire)- Similar to USB; allows up to 63 devices to be connected at a time
IrDA port- Use infrared signal; No physical connection
VGA connector- A 15 pin connector used for monitors
Telephone, Network, PC card, and Sound connectors

32. Types of ports/connectors

33. What’s the difference between serial and parallel ports?

34. Processing Data

35. How does a computer represent data?
Electronic signals or impulses
Two types of signals
Analog- Continuous waveform; Examples- talking and computerized gas pumps.
Digital- On/off electrical states (bit); Examples- light switches and transistors; Most computers use digital signals.
Digital
Analog
OFF ON ON
OFF

36. What are bits and bytes of data?
Bit (Binary digit)- On or off state of electric current; Basic unit of information; Represented by 1’s and 0’s (binary numbers).
Byte- Eight bits grouped together to represent a character (Alphabetical letters, numbers and punctuation symbols); 256 different combinations.
OFF ON OR
= 1 bit 1
= 1 Byte 1 1 1 OR
= 1 Byte 1 1

37. What are character codes?
Numerical data, that computers use, translated into characters readable by humans.
American Standard Code for Information Interchange (ASCII)- Eight bits; Used by minicomputers and personal computers
Extended Binary Coded Decimal Interchange Code (EBCDIC)- Eight bits; Used by mainframe computers
Unicode- Uses 16 bits; over 65,000 combinations 1
= 4 1
= A

38. What are kilobits, megabits and gigabits?
Terms that describe units of data
Used for measuring data transfer rate (bits per second). Example- 56kbps Modem
1000 bits = 1 kilobit (kb)
1,000,000 bits = 1 megabit (mb)
1,000,000,000 bits = 1 gigabit (gb)

39. What are Kilobytes, Megabytes, Gigabytes and Terabytes?
Terms that describe units of data
Used to measure data storage. Example- 20 GB hard drive
8 bits = 1Byte
1024 Bytes = 1 Kilobyte (KB)
1,048,576 Bytes = 1 Megabyte (MB)
1,043,741,824 Bytes = 1 Gigabyte (GB)
1,099,511,627,776 Bytes = 1 Terabyte (TB)

40. THE
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