1. Inside the System Unit Lesson 2 What You Will Learn
Components found inside the system unit
Components found on the motherboard
How the CPU processes data
Characteristics of a microprocessor’s performance
Types of memory
Purpose and types of expansion buses
Types of physical connectors on the exterior of the unit
Terminology used to describe how much data computers transfer or store
Differences between analog and digital electrical impulses

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
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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
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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
Core 2 Duo
Pentium D
Pentium IV
Celeron
Advanced Micro Devices (AMD)
Athlon 64 X2 Dual-Core
Athlon
Sempron

10. Dual Core

11. 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
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12. 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

13. How a CPU works
Control unit
ALU
DECODE
EXECUTE
Memory
FETCH
STORE

14. What determines a CPUs performance?
Operations per cycle (clock speed)- The number of clock cycles per second measured in Megahertz (MHz) or Gigahertz (GHz)
Bus Speed- The speed at which data travels through the pathways between the CPU and other devices measured in Megahertz (MHz)
Cache- special high speed storage area used to speed up the memory retrieval process for the CPU, very fast and very expensive
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

15. Memory

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

17. 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.

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

19. DIMM
RIMM
NOTEBOOK DIMM
SIMM

20. Modern RAM Types DDR Type PC Name Front Side Bus
Single-Channel Mode DDR Bandwidth
Dual-Channel Mode DDR Bandwidth
DDR266
PC 2100
133MHz
2,100 MB/s
4,200 MB/s
DDR333
PC 2700
166MHz
2,700 MB/s
5,400 MB/s
DDR400
PC 3200
200MHz
3,200 MB/s
6,400 MB/s
DDR533
PC 4200
266MHz
8,400 MB/s
DDR2-400
PC2-3200
DDR2-533
PC2-4300
4,266 MB/s
8,533 MB/s
DDR2-667
PC2-5300
333MHz
5,333 MB/s
10,666 MB/s
DDR2-800
PC2-6400
400MHz
12,800 MB/s

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

31. Outside the System Unit

32. 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
Power cord
Mouse
Drive bays
Keyboard
Printer
On/off switch
Reset button
Speakers
Indicator lights
Monitor
Network
Phone Line

33. 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

34. Types of ports/connectors

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

36. Processing Data

37. 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

38. 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

39. 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

40. 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)

41. Unit
Amount
Term
Byte 1
Kilobyte KB
1.000
Thousand
Megabyte MB
1,000,000
Million
Gigabyte GB
1,000,000,000
Billion
Terabyte TB
1,000,000,000,000
Trillion
Megahertz MHz
Gigahertz GHz

42. THE
END