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

What You Will Learn

Inside the System Unit

Lesson 2

What is the system unit?

A boxlike case that houses the computer’s main hardware components

What are the different types of system units?

DesktopsNotebook

Personal Digital Assistant

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

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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The MotherboardMicroprocessor

Keyboard / Mouse Ports

Printer Port

Video Port

PCI Slots

Memory Slots

AGP Slot

Chipset

What are the types of CPUs?

Intel

Advanced Micro Devices (AMD)

Pentium IVCore 2 Duo Pentium D

AthlonAthlon 64 X2 Dual-CoreSempron

Celeron

Dual Core

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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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

Control unit ALU

Memory

How a CPU works

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

What is memory?

A term for a device that enables the computer to retain (store) information.

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.

What is Random Access Memory / RAM?

A type of volatile memory that stores information temporarily so that it’s available to the CPU.

DIMM

SIMM

NOTEBOOK DIMM

RIMM

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 4,200 MB/s 8,400 MB/s DDR2-400 PC2-3200 200MHz 3,200 MB/s 6,400 MB/s DDR2-533 PC2-4300 266MHz 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 6,400 MB/s 12,800 MB/s

HOW DOES RAM WORK?

CHIPS CONTAIN MEMORY LOCATIONS CALLED MEMORY ADDRESSES

THE CPU STORES AND RETRIEVES DATA BY GOING TO THE MEMORY ADDRESSES

Intel

WEB

KEYBOARD

CPU

RAM

MONITOR

CLICK TO BEGIN ANIMATION

HOW RAM WORKS

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

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

What is a chipset?

A collection of chips that work together

Provides circuitry to move data to and from the rest of the computer

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

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

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

Drive bays

On/off switch

Reset button

Indicator lights

FRONTBACK

Mouse

Keyboard

Power cord

Printer

Speakers

Monitor

Network

Phone Line

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

Types of ports/connectors

What’s the difference between serial and parallel ports?

SERIAL PARALLEL

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.

Analog

ON OFF

Digital

OFFON

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

0 1

OR = 1 bit

0 1

0

0 0 001 1

0 0 0 0 01 1

OR

= 1 Byte

= 1 Byte

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

0 10 0 001 1

0 0 0 0 0 01 1

= 4

= A

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)

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 1,000,000 Million

Gigahertz GHz 1,000,000,000 Billion

THE

END