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Hardware Spotlight

building a computer

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Tips for Buying Barebones Computers

Building a Computer From the Bottom Up

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Build Your Own Computer or Buy?

Building A Computer - Picking Components

Computer Peripherals

How To Maintain Your Computer!

Warning Signs of a Computer Breakdown!

Laptop or Desktop - The Debate Continues!

Tips on using Bluetooth Enabled Printers!


PC Repair Guide

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A Plus Study Guide By Domain

Domain 1.0 Installation, Configuration and

Upgrading

Domain focuses on the knowledge and skills necessary to identify, install, configure and
upgrade microcomputer components (Field Replacement Units).

Interrupt Request Settings (IRQ) Settings

The various devices in your computer, such as video, sound cards the items on the motherboard, your modem, etc. and some things that are attached to your computer share system resources.  IRQs are basically signals that are sent from one part of your PC to another indicating that some special action or attention is needed from the processor (CPU).

Each computer has 15 IRQs ranging from 0 to 15 and only one device can use an IRQ at one time.  If more than one device is trying to use an IRQ, then a conflict will occur, meaning one of the devices will cease to function properly.  Listed below are the IRQs and their respective attached devices:

IRQ

Device Type Notes
0 System Timer *
1 Keyboard *
2 Video Card This will vary
3 COM2 & C0M4 Beware of PDA's conflicting with modems
  COM1 & COM3 Beware of PDA's conflicting with modems
5 Available (LPT2 or Sound Card) *
6 Floppy Disk Controller *
7 LPT1 *
8 Real Time Clock *
9 Redirected IRQ2 Sometimes you will find network Cards here
10 Available Sometimes you will find network Cards here
11 Available *
12 PS/2Mouse *
13 Math Co-Processor *
14 Hard Disk Controller Primary disk controller on most new systems
15 Available Secondary disk controller on most new systems



I/O Address Settings

Every device within a PC must have its own unique address, hence I/O settings.  The I/O address points to the location in memory that is assigned to a particular device.  This address is expressed in hexadecimal (h).  Ranges appear below:

I/O Address Range   Device or Port Normally Assigned
000-00Fh   DMA channels 0-3
020-021h   IRQ 0-7 interrupt controller
060h, 061h   Keyboard
0F0-0FFh   Match coprocessor
130-14Fh   SCSI host adapter
170-177h   Secondary hard disk controller
1F0-1F7h   Primary hard disk controller
200-207h   Game Controller or Game Port
210   Game I/O
220-22Fh   Soundcard
278-27Fh   LPT2 or LPT3
2E8-2EFh   COM4
2F8-2FFh   COM2
300-30Fh   Network cards
320-32F   Hard Disk Controller, (8-bit ISA only)
3B0-3BBh   VGA video adapter
3C0-3DFh   VGA video adapter
378-37Fh   LPT1 or LPT2
3B0-3BF   Monochrome Graphics Adapter (MGA)
3D0-3DF   Color Graphics Adapter (CGA)
3E8-3EFh   COM3
3F0-3F7h   Floppy Controller or Primary disk adapter
3F8-3FFh   COM1
     



Serial Devices and Communication

This process uses RS-232C port standard with DB9 or DB25 to transmits data sequentially over a single conductor either synchronously or asynchronously.

Primary Synchronous Controls Signals Purpose
Serial Data Out (TxD)    Used to transmit data
Serial Data Receive (RxD)    Used to receive data
Data Terminal Ready (DTR)    Used to tell receiver that the data is ready to be sent. Connected to the DSR on the receiving hardware.
Data Set Ready    Used on the Receiver to indicate it is ready
System Ground    Ground references voltage between two devices

 

Parallel Communication Devices

Transmits data over eight conductors in parallel. Signals are either control signals or data
signals. Control signals are used to synchronize the devices (Handshaking).

Primary Parallel Signals Purpose
Acknowledgement Used to inform the transmitting device that data was received and the receiver is ready for more
Auto Feed    Used to inform the printer to generate an auto line feed
Busy    Used to Inform sender that receiver is busy
Error    Used by receiver to indicate an error
Init    Used by sender to initialize the receiver
Slct    Used by the receiver to acknowledge a Slctln
Slctln    Used by the sender to select a device
Strobe Asserted    Used by the receiver to inform that data is present on the lines

 

Types of Connectors

Connectors are either Male (Pins) or Female (sockets).

Type Description
DB9    Trapezoid, Video display and Serial ports.
DB25    Trapezoid, Parallel and Serial ports.
RJ-11    Phone line, 4 Wires UTP.
RJ-14    Dual line phone jacks, Not Common
RJ-45    Network Connectors, 8 Wire UTP
PS2/MINI-DIN    PS/2 Mouse and Keyboards, pins and one guider.

Serial Ports are Male on the PC (DB9 or DB25)
Parallel Pods are Female on the PC (DB25)
Video is Male on the PC (DB9)
Mini/DIN is Female on the PC (PS/2)

Characteristics of IDE Devices

Integrated Drive Electronics are controllers for Hard Drives. CD-ROMS and any other
compliant device.

  • The Controller is on the device itself.
  • Early IDE devices had a limitation of 528MB, now hard drives can come as large as 80 Gigabytes
  • Uses 40 Pin cables (floppy uses 34)
  • The primary drive is considered the Master and any other drive attached is said to be the Slave drive.

SCSI Devices

Small Computer Systems Interface allows you to connect multiple devices to one cable. The
Card is the controller so it removes overhead from the Drive itself and the CPU.

Type  
SCSI-1    8 Bit Bus, DB-25 or Centronics-50, 5MBps, Device 0 to 7
SCSI-2    Better
Wide    16 Bit Bus, Device 0 to 15
Fast    10MBps,Dovice 0 to 7
Fast-Wide    16 Bit Bus, 20MBps, Device 0 to 15
SCSI-3    16 Bit Bus. 40MBps, Device 0 to 15

Notes:

  • The adapter is always given the ID of 0 on PS/2 machines or ID 7 for most others
  • The first hard disk is ID 1 on PS/2 and ID 0 for most others
  • CD-ROM devices are ID 3
  • Slower devices are given slower ID's
  • Internal SCSI uses 50 pin ribbon connectors
  • External cables are female DB-25, Centronics 50, mini-50, or mini-68
  • Both ends of the cable must be terminated

Some devices have inbuilt termination which can be set via jumpers.


BIOS

The Basic Input-Output System (BIOS):

  • Contains the system settings for the computer
  • Is stored on Read Only Memory (ROM) on a memory chip located on the motherboard
  • The settings are removed from BIOS when you turn the computer off, but are restored from the CMOS (Complimentary metal Oxide Semi-Conductor) at boot time
  • The CMOS is powered by the battery
  • Flash BIOS means that the BIOS can be upgraded via a software Flash Program from the
    BIOS vendor
  • Removable BIOS means that to Upgrade you have to physically remove and replace the
    BIOS chip

 

Domain 2.0 Diagnosing and Troubleshooting

This domain deals with diagnosing and resolving various FRU problems

POST Audible / Visible Error Codes

The Power On Self Test occurs every time you boot (turn on) your computer. Its purpose is to help diagnose system related problems that are found in hardware or BIOS.  In most cases, anything other than a single beep indicates a fault or problem.

Error Range    Component Effected
100-199    System Board Problem
200-299    Memory Error
300-399    Keyboard Problem
400-499    Video Problems, Monochrome
500-599    Video problems, Color
600-699    Floppy Disk Errors
1 700-1799    Hard Disk Problems

Common Error Codes

Error Code    Error Message    Description
161    CMOS Battery Failure    CMOS Battery needs to be replaced
164    Memory Size Error    Occurs after a memory pc is struggling with configuration
201    Memory Test Failed    One or more of the RAM Chips failed
301    Keyboard Did Not Respond    Indication that the keyboard may need cleaning
303    Keyboard or System Unit Error    Indicates a bad keyboard that needs to be replaced
423    Parallel Port test failed    Reported with Monochrome adapters. May need to replace the adapter.

 

Domain 3.0 Preventive Maintenance


This domain is concerned with preventive maintenance, safety and disposal requirements.

Cleaning

  • Liquid cleaning compounds such as isopropyl alcohol can be used to clean contacts and
    read/write heads via a cleaning diskette
  • Rubber knives can be used to remove hardened residue. metal knives should never be used
  • Always vacuum out the case whenever you get the chance to reduce the build up of dust and also static electricity.


Power Issues

  • Brownouts occur when there is not enough power to operate an electrical device
  • Power Spikes are huge increases in electrical current for a split second
  • Power Surge are similar to a spike but lower power


UPS

A UPS protects your PC from brownouts, spikes, surges and dirty current. This is
accomplished by several components in the UPS such as suppressers. noise filters, and
surge protectors.  Suppressers - Absorbs or blocks the spike and protects against surges.
Noise Filters - Noise caused by Electro-Magnetic Interference (EMI) is reduced


Monitors (CRT)

Monitors are high voltage components. Never wear an ESD wrist strap when handling
monitors. To discharge a monitor, connect a wire around the screwdriver and ground the wire. Use the screwdriver to pry the anode lead from the back of the CRT.


Disposal Procedures

Item Procedure
Batteries    Batteries should be disposed of in accordance with guidelines issued for your region. Never through them in the household waste.
Toner Kits    Toner cartridges are recyclable. Normally the vendor will take these from you.
Computers    Give away to charity or contact a specialist


Electro-Static Discharge

This can cause catastrophic damage where the device is inoperable or it can cause
degradation in a component which may still perform.  Hidden ESD is a static discharge that you can not feel. You only feel ESD above 30,000 volts however components can still be damaged below 30.000 volts.

To protect against ESD you should use anti-static mats, bags and an ESD wrist strap. You can
ground the wrist strap to the earth pin on a wall socket.  Make sure that you also remove all metallic jewelry.  Also bear in mind, that "Humidity below 50% leads to static".

 

Domain 4.0 Motherboard / Processors /

Memory

This domain is concerned with terminology and classifications of hardware.

CPU Chips

8088
Used an 8-bit bus and ran at 4.77Mhz

386
Could handle up to 16MB of memory.
3868X had a l6bit data bus and operated at 16.20,25, and 33MHz
386DX had a 32bit data bus and operated at 16,20,25, and 33MHz

486
Four types the SX, DX, DX2 and DX4.
The bus for all is 32bit. An 8bit on chip cache was introduced.  Also, a Math Co-Processor was
in-build but disabled on the SX.

586 (Pentium Class)
64b1t data bus, l6bit cache. Combines two 486DX chips into one using the Dual Independent
Bus Architecture resulting in true parallel processing. Heat sinks were required due to the
large amount of heat generated.

686 (Pentium II Class)
Integrated MMX technology.
Uses Slot 1 instead of a socket

Microprocessor Characteristics

CPU DATA BUS (BITS) ADDRESS BUS (BITS) Socket Type Pin Out MAXIMUM SPEED
8080 8 8 DIP   8
8086 16 16 LLC,PGA,PLCC   8
8088 8 8 PGA   8
80286 16 24 PGA   20
           
386DX 32 32 PGA   40
386SX 16 24 PGA   25
           
486DX 32 32 PGA   50
486SX 32 32 PGA   33
486DX2 32 32 PGA   66
486DX4 32 32 PGA   100
           
Pentium 64 32 PGA   166
Pentium MMX 64 32 PGA   200
Pentium Pro 64 32 PGA   200
Pentium II 64 64 SEC   350+
Pentium III         1.3 GHz+
Pentium 4         2.0 GHz+
           
           
           



Random Access memory (RAM)

Static RAM (SRAM)
SRAM doesn't have to be constantly refreshed. Uses a lot of power. Used in old IBM XI
machines and was limited to 2561< per chip.

Dynamic RAM (DRAM)
DRAM use capacitors instead of transistors and switches. Needs constant refresh.

Windows RAM (WRAM)
Specific to speed up graphical windows operations.

Extended Data Output RAM (EDO RAM)
Has a cache on the chip and is 10-15% faster Than DRAM. Requires a special motherboard.

Memory comes in 30 or 72 pin SIMMs or 168 pin DIMMS


Bus Architectures

Industry Standard Architecture (ISA)
This was introduced on AT computers.
Allowed a 1 6-bit data bus.
Used in 266 and 3865X PC's

Extended Industry Standard Architecture (EISA)
Introduced to compete against IBM's MCA.
Uses a 32-bit data bus.
Used in 386DX and 486 PCI

Peripheral Component Interconnect (PCI)
Designed to use Pentium Processors
Uses a 64-bit data bus.
Uses a bridge circuit to be processor independent.

Universal Serial Bus (USB)
A new technology for Plug and Play devices allowing up to 12Mbps and up to 127 simultaneous connections.

VESA Local Bus (VL_Bus)
Used for Video cards on top of EISA, a very long video card.

Personal Computer Memory Card International Association (PCMCIA)
Now called PC Card.
Used in Laptops.
Currently only 16-bit data bus

Domain 5.0 Printers

This domain requires knowledge of basic types of printers, concepts and how they work.

Printer Type Characteristics
Daisy Wheel Printers    Uses impact method to imprint a character from a daisy wheel. Similar to a typewriter in operation. Excellent quality for text but no graphics. Uses a Ribbon
Dot Matrix Printers    Uses a matrix of pins to Imprint an image. Uses a Ribbon. ROM programs the Fonts
Bubble Jet Printers    Non Contact therefore quiet. Works by spraying ink onto the paper in a sequential fashion.  Similar in operation to a dot matrix printer
Laser Printers Uses a Page Description Language (PDL) to print a page at a time

Main components of a laser printer are:

Component Purpose
Cleaning Blade    This rubber blade removes excess toner off the drum after the print process has completed
Photosensitive Drum    The core of the electro photographic process. Involved in the six step EP process
Primary Corona    Wire Highly negatively charged wire erases the charge on the Photosensitive drum to make it ready for another image
Transfer Corona    A roller that contains a positively charged to pull the toner off the photosensitive drum and place It on the page
Toner    Plastic Resin. Naturally Negatively charged
Fusing Rollers    Final stage of the EP process. Bonds the toner particles to prevent smearing. Uses heat to bond


Electro photographic Print Process (EP)

The process concerned with putting the image on the page. Follows Six steps:

Step Purpose
Cleaning    The drum is cleaned and electrically erased
Charging    The Drum is negatively charged to -5000Vdc. Done by the Primary Corona
Writing    The Laser sweeps the length of the drum applying the image. The Laser reduces the negative charge on the drum where the image is going to be.
Developing    The Toner is transferred to the area on the drum which has been swept by the laser
Transferring    Once the image is on the drum the paper is fed through and the transfer corona wire attracts the image from the drum to the paper
Fusing    The Fusing rollers heat up and pass the paper through bonding the toner to the paper. Uses a Non stick roller surface


Troubleshooting Printers

Problem Cause
Blank Pages    Can be caused by No Toner, Transfer Corona Failure or HVPS Failure
Speckled Pages    Due to a failure in the cleaning step of the EP Process. Or a scratch on the EP drum
Ghosted Images    Caused if the erasure lamp doesn't erase all of the image horn the EP drum before the next page is printed
Smudged Images    The fusing process must have failed. The heating elements in the fusing rollers may be faulty
Bubble Jet Printers    Never refill cartridges which are causing problems. The head is part of the cartridge so replace the entire cartridge.

 

Domain 6.0 Basic Networking

Coming Soon