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

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

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

Inside the System Unit

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 Click N Learn

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

Microprocessor (CPU)

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

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 Click N Learn

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

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

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

Memory

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 RIMM NOTEBOOK DIMM SIMM

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

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

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

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

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

Buses

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

Outside the System Unit

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

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?

Processing Data

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

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

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

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 Gigahertz GHz

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