CompTIA – A+ Certification Exam Prep and Review
Northbridge & Southbridge:
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RAM:
2
RAID:
1.1.1.2 Power Supplies - Power Supply Cable Color Code
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1.1.1.2 Power Supplies – Power Connector Types
Molex keyed connector connects:
 Optical drives
 Hard drives
Molex Power Connector
Berg keyed connector connects:
 Floppy drive. A
 Berg connector is smaller than a Molex connector
Berg Connector
SATA keyed connector connects
 Optical drive or a hard drive.
 SATA connector is wider and thinner than a Molex connector
 15 pins.
SATA Connector
A 20-pin or 24-pin slotted power connector connects to the motherboard.
 The 24-pin connector has two rows of 12 pins each
 20-pin connector has two rows of 10 pins each.
24 Pin Motherboard Power Connector
A 4-pin to 8-pin auxiliary power connector has two rows of two to four pins and supplies power to all
areas of the motherboard. The auxiliary power connector is the same shape as the main power connector
but smaller. It can also power other devices within the computer.
4 Pin Auxiliary Power Connector
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6/8-pin PCIe power connector has two rows of three to four pins and supplies power to other internal
components.
6 Pin PCIe Power Connector
1.1.2.4 ROM – ROM Types:
ROM - Read-only memory chips. Information is written to a ROM chip when it is manufactured. A ROM
chip cannot be erased or re-written and is obsolete.
PROM - Programmable read-only memory. Information is written to a PROM chip after it is
manufactured. A PROM chip cannot be erased or re-written.
EPROM - Erasable programmable read-only memory. Information is written to an EPROM chip after it is
manufactured. An EPROM chip can be erased with exposure to UV light. Special equipment is required.
EEPROM - Electrically erasable programmable read-only memory. Information is written to an EEPROM
chip after it is manufactured. EEPROM chips are also called Flash ROMs. An EEPROM chip can be erased
and re-written without having to remove the chip from the computer.
NOTE: ROM is sometimes called firmware. This is misleading, because firmware is actually the software
that is stored in a ROM chip.
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1.1.2.5 RAM- RAM Types
DRAM - Dynamic RAM is a memory chip that is used as main memory. DRAM must be constantly
refreshed with pulses of electricity in order to maintain the data stored within the chip.
SRAM - Static RAM is a memory chip that is used as cache memory. SRAM is much faster than DRAM
and does not have to be refreshed as often. SRAM is much more expensive than DRAM.
FPM Memory - Fast Page Mode DRAM is memory that supports paging. Paging enables faster access to
the data than regular DRAM. FPM memory was used in Intel 486 and Pentium systems.
EDO Memory - Extended Data Out RAM is memory that overlaps consecutive data accesses. This speeds
up the access time to retrieve data from memory, because the CPU does not have to wait for one data
access cycle to end before another data access cycle begins.
SDRAM - Synchronous DRAM is DRAM that operates in synchronization with the memory bus. The
memory bus is the data path between the CPU and the main memory. Control signals are used to
coordinate the exchange of data between SDRAM and the CPU.
DDR SDRAM - Double Data Rate SDRAM is memory that transfers data twice as fast as SDRAM. DDR
SDRAM increases performance by transferring data twice per clock cycle.
DDR2 SDRAM - Double Data Rate 2 SDRAM is a faster than DDR-SDRAM memory. DDR2 SDRAM
improves performance over DDR SDRAM by decreasing noise and crosstalk between the signal wires.
DDR3 SDRAM - Double Data Rate 3 SDRAM expands memory bandwidth by doubling the clock rate of
DDR2 SDRAM. DDR3 SDRAM consumes less power and generates less heat than DDR2 SDRAM.
RDRAM - RAMBus DRAM is a memory chip that was developed to communicate at very high rates of
speed. RDRAM chips are not commonly used.
1.1.2.6 Memory Modules – Memory Module Types
DIP - Dual Inline Package is an individual memory chip. A DIP has dual rows of pins used to attach it to
the motherboard.
SIMM - Single Inline Memory Module is a small circuit board that holds several memory chips. SIMMs
have 30-pin or 72-pin configurations.
DIMM - Dual Inline Memory Module is a circuit board that holds SDRAM, DDR SDRAM, DDR2 SDRAM,
and DDR3 SDRAM chips. There are 168-pin SDRAM DIMMs, 184-pin DDR DIMMs, and 240-pin DDR2 and
DDR3 DIMMs.
RIMM - RAMBus Inline Memory Module is a circuit board that holds RDRAM chips. A typical RIMM has a
184-pin configuration.
SODIMM - Small Outline DIMM has a 72-pin and 100-pin configurations for support of 32-bit transfers
or a 144-pin, 200-pin, and 204-pin configurations for support of 64-bit transfers. This smaller, more
condensed version of DIMM provides random access data storage that is ideal for use in laptops,
printers, and other devices where conserving space is desirable.
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1.1.2.5 RAM- Common Memory Types Characteristics
Note: One way to remember memory bus speeds is to look at the number in the RAM module name.
DDR2 type memory is always twice the front side bus speed. So if the memory module is called DDR2400 it would mean the front side bus speed would half of the memory speed which would be 200 MHZ.
With DDR2 just divide the Memory Module speed in half to find the front side bus speed in MHZ. All
other memory type will have the bus speed in the memory module speed name
1.1.2.7 Adapter Cards and Expansion Slots
PCI
AGP
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PCIe
PCI-X
Mini PCI
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1.1.2.8 Storage Devices and RAID – Level Types:
1.1.2.8 Storage Devices – Types of Drive Interfaces

IDE - Integrated Drive Electronics, also called Advanced Technology Attachment (ATA), is an early
drive controller interface that connects computers and hard disk drives. An IDE interface uses a 40pin connector.

EIDE - Enhanced Integrated Drive Electronics, also called ATA-2, is an updated version of the IDE
drive controller interface. EIDE supports hard drives larger than 512 MB, enables Direct Memory
Access (DMA) for speed, and uses the AT Attachment Packet Interface (ATAPI) to accommodate
optical drives and tape drives on the EIDE bus. An EIDE interface uses a 40-pin connector.

PATA - Parallel ATA refers to the parallel version of the ATA drive controller interface.

SATA - Serial ATA refers to the serial version of the ATA drive controller interface. A SATA interface
uses a 7-pin data connector.
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
eSATA - External Serial ATA provides a hot-swappable, external interface for SATA drives. Hotswapping is the ability to connect and disconnect a device while a computer is powered on. The
eSATA interface connects an external SATA drive using a 7-pin connector. The cable can be up to
6.56 ft (2 m) in length.

SCSI - Small Computer System Interface is a drive controller interface that can connect up to 15
drives. SCSI can connect both internal and external drives. An SCSI interface uses a 25-pin, 50-pin,
or 68-pin connector.
1.1.2.9 Internal Cables:

Floppy disk drive (FDD) data cable - Has up to two 34-pin drive connectors and one 34-pin
connector for the drive controller.
Floppy Disk Drive Data Connector Cable

PATA (IDE/EIDE) 40-conductor data cable - Originally, the IDE interface supported two devices on
a single controller. With the introduction of Extended IDE, two controllers capable of supporting
two devices each were introduced. The 40-conductor ribbon cable uses 40-pin connectors. The
cable has two connectors for the drives and one connector for the controller.
Hard Drive - PATA 40 PIn Data Cable

PATA (EIDE) 80-conductor data cable - As the data rates available over the EIDE interface
increased, the chance of data corruption during transmission increased. An 80-conductor cable
was introduced for devices transmitting at 33.3 MB/s and over, allowing for a more reliable
balanced data transmission. The 80-conductor cable uses 40-pin connectors.

SATA data cable - This cable has seven conductors, one keyed connector for the drive, and one
keyed connector for the drive controller.
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Hard Drive - SATA Data Cable

SCSI data cable - There are three types of SCSI data cables. A narrow SCSI data cable has 50
conductors, up to seven 50-pin connectors for drives, and one 50-pin connector for the drive
controller, also called the host adapter. A wide SCSI data cable has 68 conductors, up to 15 68-pin
connectors for drives, and one 68-pin connector for the host adapter. An Alt-4 SCSI data cable has
80 conductors, up to 15 80-pin connectors for drives, and one 80-pin connector for the host
adapter.
1.1.3.1 Video Ports and Cables – External Cables
Go to page 1.1.3.1 and 1.1.3.2 in the cisco content to see pictures of many different external cables and
their characteristics
1.1.4.2 Output Devices – Monitor Types:

CRT - The cathode-ray tube (CRT) has three electron beams. Each beam is directed at colored
phosphor dots on the screen that glow red, blue, or green when struck by the beam. Areas not
struck by an electron beam do not glow. The combination of glowing and non-glowing areas
creates the image on the screen. Some televisions use this technology. CRTs usually have a degauss
button on the front that the user can press to remove discoloration caused by magnetic
interference.

LCD - Liquid crystal display (LCD) is commonly used in flat panel monitors, laptops, and some
projectors. It consists of two polarizing filters with a liquid crystal solution between them. An
electronic current aligns the crystals so that light can either pass through or not pass through. The
effect of light passing through in certain areas and not in others is what creates the image. LCD
comes in two forms, active matrix and passive matrix. Active matrix is sometimes called thin film
transistor (TFT). TFT allows each pixel to be controlled, which creates very sharp color images.
Passive matrix is less expensive than active matrix but does not provide the same level of image
control. Passive matrix is not commonly used in laptops.

LED - A light-emitting diode (LED) display is an LCD display that uses LED backlighting to light the
display. LED has lower power consumption than standard LCD backlighting, allows the panel to be
thinner, lighter, brighter, and display better contrast.

OLED - An organic LED display uses a layer of organic material that responds to electrical stimulus
to emit light. This process allows each pixel to light individually, resulting in much deeper black
levels than LED. OLED displays are also thinner and lighter than LED displays.

Plasma - Plasma displays are another type of flat panel monitor that can achieve high levels of
brightness, deep black levels, and a very wide range of colors. Plasma displays can be created in
sizes of up to 150 in (381 cm) or more. Plasma displays get their name from the use of tiny cells of
ionized gas that light up when stimulated by electricity. Plasma displays are often used in home
theater applications because of their accurate representation of video.

DLP - Digital Light Processing (DLP) is another technology used in projectors. DLP projectors use a
spinning color wheel with a microprocessor-controlled array of mirrors called a digital micromirror
device (DMD). Each mirror corresponds to a specific pixel. Each mirror reflects light toward or away
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from the projector optics. This creates a monochromatic image of up to 1024 shades of gray in
between white and black. The color wheel then adds the color data to complete the projected
color image.
1.2.1.10 Selecting Input and Output Devices:
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4.1.1.2 Preventive Maintenance Tasks – Hardware
Use these tasks as a guide to creating a hardware maintenance program:
 Remove dust from fan intakes.
 Remove dust from the power supply.
 Remove dust from the components inside the computer and peripheral equipment such as
printers.
 Clean the mouse, keyboard, and display.
 Check for and secure any loose cables.
4.1.1.2 Preventive Maintenance Tasks – Software
Use these tasks as a guide to creating a software maintenance schedule that fits the needs of your
computer:
 Review and install the appropriate security updates.
 Review and install the appropriate software updates.
 Review and install the appropriate driver updates.
 Update the virus definition files.
 Scan for viruses and spyware.
 Remove unwanted or unused programs.
 Scan hard drives for errors.
 Defragment non-SSD hard drives.
4.1.1.3 Clean the Case and Internal Components – Remove Accumulated Dust
When dust accumulates inside the computer, it prevents the flow of air and reduces the cooling of
components. Several components are important to keep clean:
 Heat sink and fan assembly
 RAM
 Adapter cards
 Motherboard
 Fans
 Power supply
 Internal drives
To remove dust from the inside of a computer, use a combination of compressed air, a low-air-flow ESD
vacuum cleaner, and a small lint-free cloth.
4.2.1.1 Introduction to Troubleshooting – First Thing To Do
Always perform a backup before beginning any troubleshooting. You must protect data before
beginning any work on a customer’s computer. If your work results in data loss for the customer, you or
your company could be held liable.
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4.2.1.2 Identify the Problem – Step One
Open-Ended and Closed-Ended Questions
Open-ended questions allow customers to explain the details of the problem in their own words. Use
open-ended questions to obtain general information. Based on the information from the customer, you
can proceed with closed-ended questions. Closed-ended questions generally require a yes or no answer.
These questions are intended to get the most relevant information in the shortest time possible.
4.2.1.3 Establish a Theory of Probable Cause – Step Two
4.2.1.4 Test the Theory to Determine Cause – Step Three
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4.2.1.5 Establish a Plan of Action to Resolve the Problem and Implement the Solution – Step Four
4.2.1.6 Verify Full System Functionality and, If Applicable, Implement Preventive Measures – Step Five
4.2.1.7 Document Findings, Actions, and Outcomes – Step Six
4.2.2.1 PC Common Problems and Solutions
Common hardware problems include the following:
 Storage Device - Storage device problems are often related to loose or incorrect cable connections,
incorrect drive and media formats, and incorrect jumper and BIOS settings, as shown in Figure 1.
 Motherboard and Internal Component- These problems are often caused by incorrect or loose
cables, failed components, incorrect drivers, and corrupted updates, as shown in Figure 2.
 Power Supply - Power problems are often caused by a faulty power supply, loose connections, and
inadequate wattage, as shown in Figure 3.
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
CPU and Memory - Processor and memory problems are often caused by faulty installations,
incorrect BIOS settings, inadequate cooling and ventilation, and compatibility issues, as shown in
Figure 4.
6.1.1.1 Define Computer Networks
Network devices link together using a variety of connections:
 Copper cabling - Uses electrical signals to transmit data between devices
 Fiber-optic cabling - Uses glass or plastic fiber to carry information as light pulses
 Wireless connection - Uses radio signals, infrared technology, or satellite transmissions
6.2.1.1 LANs
6.2.1.2 WLANs
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6.2.1.5 WANs
6.2.1.7 Client/Server Networks
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6.2.1.8 Activity - Matching Network Types
6.3.1.1 Bandwidth - Measurements
Bandwidth is measured in bits per second and is usually denoted by any of the following units of
measure:




b/s - bits per second
kb/s - kilobits per second
Mb/s - megabits per second
Gb/s - gigabits per second
NOTE: 1 byte is equal to 8 bits, and is abbreviated with a capital letter B. 1 MB/s is approximately 8
Mb/s.
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6.3.1.2 Data Transmission
6.3.2.2 IPv4 – Address Ranges
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IPv4 Subnet Mask:
The subnet mask indicates the network portion of an IPv4 address. Like the IPv4 address, the subnet
mask is a dotted-decimal number. Usually all hosts within a LAN use the same subnet mask. The figure
shows the default subnet masks for usable IPv4 addresses that are mapped to the first three classes of
IPv4 addresses:
 255.0.0.0 - Class A, which indicates that the first octet of the IPv4 address is the network portion
 255.255.0.0 - Class B, which indicates that the first two octets of the IPv4 address is the network
portion
 255.255.255.0 - Class C, which indicates that the first three octets of the IPv4 address is the
network portion
6.3.2.4 Static Addressing
You can assign the following IP address configuration information to a host:




IP address - identifies the computer on the network
Subnet mask - is used to identify the network on which the computer is connected
Default gateway - identifies the device that the computer uses to access the Internet or another
network
Optional values - such as the preferred Domain Name System (DNS) server address and the
alternate DNS server address
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6.3.2.5 DHCP Addressing
A DHCP server automatically assigns the following IP address configuration information to a host:




IP address
Subnet mask
Default gateway
Optional values, such as a DNS server address, as shown in Figure 2
6.3.2.6 ICMP – PING Command
Ping is commonly used to test connections between computers. Ping is a simple but highly useful
command-line utility used to determine whether a specific IP address is accessible.
The ipconfig command is another useful command-line utility used to verify that a NIC has a valid IP
address. To display full configuration information of all network adapters, type C:\> ipconfig /all in the
Command Prompt window. You can ping the IP address obtained from the ipconfig /all command to
test IP connectivity.
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6.3.3.1 TCP and UDP – Advantages & Disadvantages
Continue Next Page
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6.3.3.3 TCP and UDP Protocols and Ports
6.4.1.2 Hubs, Bridges, and Switches
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6.4.1.3 Routers and Wireless Access Points
Wireless Access Point
Integrated Service Router (ISR)
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6.4.2.1 Considerations for Cabling a Network
6.4.2.3 Twisted-Pair Cables
There are two basic types of twisted-pair cables:
 Unshielded twisted-pair (UTP) - Cable that has two or four pairs of wires. This type of cable relies
solely on the cancellation effect produced by the twisted-wire pairs that limits signal degradation
caused by electromagnetic interference (EMI) and radio frequency interference (RFI). UTP is the
most commonly used cabling in networks. UTP cables have a length up to 330 ft. (100 m.).

Shielded twisted-pair (STP) - Each pair of wires is wrapped in metallic foil to better shield the wires
from noise. Four pairs of wires are then wrapped in an overall metallic braid or foil. STP reduces
electrical noise from within the cable. It also reduces EMI and RFI from outside the cable.
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6.4.2.6 Fiber-Optic Cables
Fiber-optic cable is usually more expensive to use than copper cable, and the connectors are more costly
and harder to assemble. Common connectors for fiber-optic networks are:



SC - 2.5 mm ferrule that uses a snap-in connector that latches with a simple push-pull motion
ST - 2.5 mm ferrule that uses a bayonet mount connector that is spring loaded
LC - 1.25 mm ferrule that uses a snap-in connector that latches with a simple push-pull motion
These are the two types of glass fiber-optic cable:


Multimode - Cable that has a thicker core than single-mode cable. It is easier to make, can use
simpler light sources (LEDs), and works well over distances up to 6,560 ft (2 km). It often uses LEDs
as the light source within LANs or distances of 200 meters within a campus network.
Single-mode - Cable that has a very thin core. It is harder to make, uses lasers as a light source, and
can transmit signals up to 62.14 mi (100 km). It often uses lasers as the light source within campus
backbones for distances of several thousand meters.
6.5.1.1 Logical and Physical Topologies – Physical Topologies
Physical Topology
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Physical Topology
6.6.1.3 Ethernet Technologies
6.6.1.4 IEEE 802.11 – Wireless
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6.7.1.1 TCP/IP
Application Layer Protocols
Application layer protocols provide network services to user applications, such as web browsers and
email programs. Common protocols that operate at the application layer include HTTP, Telnet, FTP,
SMTP, DNS, and HTML.
Transport Layer Protocols
Transport layer protocols provide end-to-end management of the data. One of the functions of these
protocols is to divide the data into manageable segments for easier transport across the network.
Common protocols that operate at the transport layer include TCP and UDP.
Internet Layer Protocols
Internet layer protocols provide connectivity between hosts in the network. Common protocols that
operate at the Internet layer include IP and ICMP.
Network Access Layer Protocols
Network access layer protocols describe the standards that hosts use to access the physical media. The
IEEE 802.3 Ethernet standards and technologies, such as CSMA/CD and 10BASE-T, are defined in this
layer.
6.7.1.2 OSI - OSI Model
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6.7.1.3 Comparing the OSI and TCP/IP Models
6.9.1.2 DSL and ADSL
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Asymmetric Digital Subscriber Line
ADSL has different bandwidth capabilities in each direction. Downloading is the receiving of data from
the server to the end user. Uploading is the sending of data from the end user to the server. ADSL has a
fast download rate which is beneficial to users who are downloading large amounts of data. The upload
rate of ADSL is slower than the download rate. ADSL does not perform well when hosting a web server
or FTP server, both of which involve upload-intensive Internet activities.
6.9.1.4 WiMAX
Worldwide Interoperability for Microwave Access (WiMAX) is an IP-based wireless 4G broadband
technology that offers high-speed mobile Internet access for mobile devices. WiMAX is a standard called
IEEE 802.16e. It supports an MAN-sized network and has download speeds up to 70 Mb/s and distances
up to 30 miles (50 km). Security and QoS for WiMAX are equivalent to cellular networks.
6.9.1.7 Selecting an ISP for the Customer
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6.11.1.1 Identify the Problem – Network Troubleshooting
6.11.1.2 Establish a Theory of Probable Cause – Network Troubleshooting
6.11.1.3 Test the Theory to Determine Cause – Network Troubleshooting
6.11.1.4 Establish a Plan of Action to Resolve the Problem and Implement the Solution – Network
Troubleshooting
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6.11.1.5 Verify Full System Functionality and Implement Preventative Measures – Network
Troubleshooting
6.11.1.6 Document Findings, Actions, and Outcomes – Network Troubleshooting
6.11.2.1 Identify Common Problems and Solutions – Network Troubleshooting
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7.2.1.1 LCD, LED, OLED, and Plasma Monitors
There are four types of laptop displays:
 LCD
 LED
 OLED
 Plasma
LED monitors use less power and have a longer lifespan than LCD monitors. Organic LED (OLED)
technology is commonly used for mobile devices and digital cameras, but can also be found in laptop
concept designs. OLED monitors will become more popular as the technology improves. Plasma displays
are rarely found in laptops, because they consume a large amount of power.
7.2.2.1 Backlights and Inverters
Inverter
An inverter and backlight are two important display components. The inverter converts DC power to the
higher voltage AC power that is required by the backlight. The backlight shines through the screen and
illuminates the display. Two common types of backlights are cold cathode fluorescent lamp (CCFL) and
LED. LED monitors use LED-based backlights that do not have fluorescent tubes or inverters. LCD
monitors use CCFL technology for the backlight. The fluorescent tube is connected to an inverter.
7.2.2.2 Wi-Fi Antenna Connectors
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7.4.1.4 Wi-Fi – Laptop
Three major types of wireless adapters are used in laptops, as shown in the figure.



Mini-PCI - Commonly used by older laptops. Mini-PCI cards have 124 pins and are capable of
802.11a, 802.11b, and 802.11g wireless LAN connection standards.
Mini-PCIe - Most common type of wireless card in laptops. Mini-PCIe cards have 54 pins and
support all wireless LAN standards.
PCI Express Micro - Commonly found in newer and smaller laptops, such as Ultrabooks, because
they are half the size of Mini-PCIe cards. PCI Express Micro cards have 54 pins and support all
wireless LAN standards.
Wireless expansion cards are not commonly used in newer laptops, because most of them have built-in
wireless adapter cards. It is more common to use a USB adapter to add or upgrade wireless capabilities
for a laptop.
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7.5.1.3 SODIMM Memory
7.7.1.1 Identify the Problem – Laptops
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7.7.1.2 Establish a Theory of Probable Cause – Laptops
7.7.1.3 Test the Theory to Determine Cause – Laptops
7.7.1.4 Establish a Plan of Action to Resolve the Problem and Implement the Solution - Laptops
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7.7.1.5 Verify Full System Functionality and Implement Preventative Measures - Laptops
7.7.1.6 Document Findings, Actions, and Outcomes – Laptops
7.7.2.1 Identify Common Problems and Solutions - Laptops
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8.1.1.3 Touchscreens – Mobile Devices
There are two types of touchscreens:
 Capacitive - Consists of a glass screen coated with a conductor. Because the human body is also a
conductor, touching the screen interrupts the electrical field of the screen. This change is
measured by the touch processor to determine the vertical and horizontal location of the touch on
the screen.
 Resistive - Consists of transparent layers of material capable of conducting electricity. These layers
have a small air gap between them. One layer conducts electricity from top to bottom, while the
other conducts electricity from left to right. When pressure is exerted on the screen, the two layers
touch. When the layers touch, the vertical and horizontal locations are calculated by the touch
processor from where the electricity is interrupted.
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8.1.1.4 Solid State Drives – Mobile Devices
SSD Board
Mobile devices use the same components found in SSDs to store data. To reduce the size requirements,
there is no case surrounding the components. The circuit board, flash memory chips, and memory
controller in SSDs are installed directly inside the mobile device. These are some of the advantages of
using flash memory storage in mobile devices:






Power efficiency - Flash memory requires very little power to store and retrieve data. This reduces
the frequency with which mobile devices need to be recharged.
Reliability - Flash memory can withstand high levels of shock and vibration without failing. Flash
memory is also highly resistant to heat and cold.
Lightweight - The weight of mobile devices is not significantly affected by the amount of memory
installed.
Compact - Because flash memory is compact, mobile devices can remain small regardless of the
amount of memory installed.
Performance - Flash memory does not have any moving parts, so there is no spin-up time for
platters like a conventional hard drive. There is also no drive head to move, reducing the seek time
to locate data.
Noise - Flash memory makes no noise.
8.5.1.1 Identify the Problem – Mobile Devices
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8.5.1.2 Establish a Theory of Probable Cause – Mobile Devices
8.5.1.4 Establish a Plan of Action to Resolve the Problem and Implement the Solution
– Mobile Devices
8.5.1.5 Verify Full System Functionality and Implement Preventive Measures – Mobile Devices
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8.5.2.1 Identify Common Problems and Solutions – Mobile Devices
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9.1.1.2 Wired Printer Connection Types
Printer Connections
Serial
Serial data transfer is the movement of single bits of information in a single cycle. A serial connection
can be used for dot matrix printers because the printers do not require high-speed data transfer.
Parallel
Parallel data transfer is faster than serial data transfer. Parallel data transfer moves multiple bits of
information in a single cycle. The data transfer path is wider than the serial data transfer path, allowing
data to move more quickly to or from the printer.
IEEE 1284 is the standard for parallel printer ports. Enhanced Parallel Port (EPP) and Enhanced
Capabilities Port (ECP) are two modes of operation within the IEEE 1284 standard that allow
bidirectional communication.
SCSI
Small Computer System Interface (SCSI) uses parallel communication technology to achieve high datatransfer rates.
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USB
USB is a common interface for printers and other devices. When a USB device is added to a computer
system that supports plug-and-play, the device is automatically detected and starts the driver
installation process.
FireWire
FireWire, also known as i.LINK or IEEE 1394, is a high-speed communication bus that is platform
independent. FireWire connects digital devices such as digital printers, scanners, digital cameras, and
hard drives.
FireWire allows a peripheral device, such as a printer, to plug directly into a computer. It also allows the
device to be hot-swappable. FireWire provides a single plug-and-socket connection that can attach up to
63 devices. FireWire has a data transfer rate of up to 400 Mb/s.
Ethernet
Connecting a printer to the network requires cabling that is compatible with both the network and the
network port installed in the printer. Most network printers use an RJ-45 interface to connect to a
network or wireless interface.
9.2.1.1 Inkjet Printers
There are two types of inkjet nozzles:
Thermal - A pulse of electrical current is applied to heating chambers around the nozzles. The heat
creates a bubble of steam in the chamber. The steam forces ink out through the nozzle and onto the
paper.
Piezoelectric - Piezoelectric crystals are located in the ink reservoir at the back of each nozzle. A charge
is applied to the crystal, causing it to vibrate. This vibration of the crystal controls the flow of ink onto
the paper.
These are some advantages of an inkjet printer:
 Initial low cost
 High resolution
 Quick to warm up
These are some disadvantages of an inkjet printer:
 Nozzles are prone to clogging.
 Ink cartridges are expensive.
 Ink is wet after printing.
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Inkjet Printer Components:
9.2.1.2 Laser Printers
A laser printer is a high-quality, fast printer that uses a laser beam to create an image. The central part
of the laser printer is its imaging drum. The drum is a metal cylinder that is coated with a light-sensitive
insulating material. When a beam of laser light strikes the drum, it becomes a conductor at the point
where the light hits it.
As the drum rotates, the laser beam draws an electrostatic image upon the drum. The undeveloped or
latent image is passed by a supply of dry ink or toner that is attracted to it. While the image is being
exposed on the drum, an individual sheet of paper has been pressed between a separation pad and
pickup roller and is fed toward the drum.
The drum turns and brings the exposed image in contact with the paper, which attracts the ink from the
drum. The paper is then passed through a fuser assembly that is made up of hot rollers, which melts the
toner into the paper.
Printing Process
The laser printer process involves seven steps to print information onto a single sheet of paper.
1. Processing - The data from the source must be converted into a printable form. The printer converts
data from common languages, such as Adobe PostScript (PS) or HP Printer Command Language (PCL), to
a bitmap image stored in the printer’s memory. Some laser printers have built in Graphical Device
Interface (GDI) support. GDI is used by Windows applications to display printed images on a monitor so
there is no need to convert the output to another format such as PostScript or PCL.
2. Charging - The previous latent image on the drum is removed and the drum is conditioned for the
new latent image. A wire, grid, or roller receives a charge of approximately -600 volts DC uniformly
across the surface of the drum. The charged wire or grid is called the primary corona. The roller is called
a conditioning roller.
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3. Exposing - To write the image, the photosensitive drum is exposed with the laser beam. Every portion
of the drum that is scanned with the light has the surface charge reduced to about -100 volts DC. This
electrical charge has a lower negative charge than the remainder of the drum. As the drum turns, an
invisible latent image is created on the drum.
4. Developing - The toner is applied to the latent image on the drum. The toner is a negatively charged
combination of plastic and metal particles. A control blade holds the toner at a microscopic distance
from the drum. The toner then moves from the control blade to the more positively charged latent
image on the drum.
5. Transferring - The toner attached to the latent image is transferred to the paper. A corona wire places
a positive charge on the paper. Because the drum was charged negatively, the toner on the drum is
attracted to the paper. The image is now on the paper and is held in place by the positive charge.
Because color printers have three cartridges of ink, a colored image must go through multiple transfers
to be complete. To ensure precise images, some color printers write multiple times onto a transfer belt
that transfers the complete image to paper.
6. Fusing - The toner is permanently fused to the paper. The printing paper is rolled between a heated
roller and a pressure roller. As the paper moves through the rollers, the loose toner is melted and fused
with the fibers in the paper. The paper is then moved to the output tray as a printed page. Laser printers
with duplex assemblies can print on both sides of a sheet of paper.
7. Cleaning - When an image has been deposited on the paper and the drum has separated from the
paper, the remaining toner must be removed from the drum. A printer might have a blade that scrapes
the excess toner. Some printers use an AC voltage on a wire that removes the charge from the drum
surface and allows the excess toner to fall away from the drum. The excess toner is stored in a used
toner container that is either emptied or discarded.
These are some advantages of a laser printer:
 Low cost per page
 High ppm
 High capacity
 Prints are dry
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These are some disadvantages of a laser printer:
 High cost of start up
 Toner cartridges are expensive
 Require a high level of maintenance
9.2.1.3 Thermal Printers
A thermal printer has the following advantages:
 Longer life because there are few moving parts
 Quiet operation
 No cost for ink or toner
A thermal printer has the following disadvantages:
 Paper is expensive.
 Paper has a short shelf life.
 Images are poor quality.
 Paper must be stored at room temperature.
 Color printing is not available.
9.2.1.4 Impact Printers
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The following are some advantages of an impact printer:
 Uses less expensive ink than inkjet or laser printers
 Uses continuous feed paper
 Has carbon-copy printing ability
The following are some disadvantages of an impact printer:
 Noisy
 Low-resolution graphics
 Limited color capability
9.4.2.1 Purposes of Print Servers
Print servers enable multiple computer users to access a single printer. A print server has three
functions:



Provide client access to print resources.
Administrate print jobs by storing them in a queue until the print device is ready for them and then
feeding or spooling the print information to the printer.
Provide feedback to users.
Hardware Print Servers
Hardware print servers allow many users on a network to access a single printer. A hardware print
server can manage network printing through either wired or wireless connections. An advantage of
using a hardware print server is that the server accepts incoming print jobs from computers, thereby
freeing the computers for other tasks. A hardware print server is always available to users, unlike a
printer shared from a user's computer.
Dedicated PC Print Servers
A dedicated PC print server handles client print jobs in the most efficient manner and can manage more
than one printer at a time. A print server must have the following resources to meet the requests of
print clients:

Powerful processor - Because the PC print server uses its processor to manage and route printing
information, it must be fast enough to handle all incoming requests.
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

Adequate hard disk space - A PC print server captures print jobs from clients, places them in a
print queue, and sends them to the printer in a timely way. This process requires the computer to
have enough storage space to hold these jobs until completed.
Adequate memory - The server processor and RAM handle sending print jobs to a printer. If server
memory is not large enough to handle an entire print job, the hard drive must send the job, which
is much slower.
Computer-shared Printers
A computer that has a printer attached can share that printer with other users on the network, as
shown in the figure. For example, in a home network, users can print documents from wherever they
are in the house by using a wireless laptop. In a small office network, sharing a printer means one
printer can serve many users.
Sharing a printer from a computer also has disadvantages. The computer sharing the printer uses its
own resources to manage the print jobs coming to the printer. If the computer user on the desktop is
working at the same time as a user on the network is printing, the desktop computer user might notice a
performance slowdown. In addition, the printer is not available to others if the user reboots or powers
off the computer with a shared printer.
9.5.1.1 Vendor Guidelines – Printer Preventative Maintenance
Preventive maintenance decreases downtime and increases the service life of the components. It is
important to maintain printers to keep them working properly. A good maintenance program
guarantees good quality prints and uninterrupted operation. The printer documentation contains
information on how to maintain and clean the equipment.
Read the information manuals that come with every new piece of equipment. Follow the recommended
maintenance instructions. Use the supplies listed by the manufacturer. Less expensive supplies can save
money, but may produce poor results, damage the equipment, or void the warranty.
CAUTION: Be sure to unplug the printer from the electrical source before beginning any type of
maintenance.
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When maintenance is completed, reset the counters to allow the next maintenance to be completed at
the correct time. On many types of printers, the page count is viewed through the LCD display or a
counter located inside the main cover.
Most manufacturers sell maintenance kits for their printers. For laser printers, the kit might contain
replacement parts that often break or wear out:
 Fuser assembly
 Transfer rollers
 Separation pads
 Pickup rollers
When you install new parts or replace toners and cartridges, visually inspect all internal components and
perform the following tasks:
 Remove bits of paper and dust
 Clean spilled ink or toner
 Look for worn gears, cracked plastic, or broken parts
9.6.1.1 Identify the Problem – Printers
9.6.1.2 Establish a Theory of Probable Cause – Printers
9.6.1.3 Test the Theory to Determine Cause – Printers
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9.6.1.4 Establish a Plan of Action to Resolve the Problem and Implement the Solution – Printers
9.6.1.5 Verify Full System Functionality and Implement Preventative Measures - Printers
9.6.2.1 Identify Common Problems and Solutions – Printers
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