By System Memory
There are two major types of memory: dynamic and static. Dynamic Random Access Memory (DRAM) loses information in the absence of power. Static RAM (SRAM) retains its data like a hard drive regardless of power state. In general, DRAM is used as system memory, and SRAM is used for cache and storage devices.
SDRAM is neither a contradiction in terms nor a type of hybrid RAM. It actually stands for Synchronous Dynamic RAM. Synchronous means that the data transfer is timed to the system clock. For many years, 168 pin SDRAM was the standard system memory. It has largely been replaced with Double Data Rate (DDR), DDR2, and DDR3. All these types of RAM use a common Dual Inline Memory Module (DIMM) form factor, but they all have unique form factors and are, therefore, not interchangeable.
Like most things on a PC, RAM is measured in speed. The motherboard must support the speed of the RAM, or the increased performance promised by the fast RAM will not be realized; or worse, the PC might not even Power On Self Test (POST).
Other Types of RAM
RAMBUS Inline Memory Module (RIMM) uses a proprietary 184-pin or 232-pin slot called a RIMM. This RAM, often called RDRAM, is found in some game console systems and a limited number of PCs. On such systems, empty RIMM slots must be filled with Continuity RIMM (CRIMM) modules.
Older Single Inline Memory Modules (SIMM) have 30 or 72 contacts on only one side. SIMMs must be installed in identical pairs.
Laptops use a small form factor called Small Outline DIMM (SODIMM). Many netbooks, Ultra Mobile PC (UMPC), and portable devices, such as cell phones and PDAs, use a MicroDIMM form factor. Figure 1-1 compares the relative size and form factors found in RAM.
VRAM is video RAM for the use of the Graphic Processing Unit (GPU). VRAM does not stand for Virtual RAM. Virtual RAM is space on the HD that the RAM uses as an overflow area and as a backup copy of the contents in case of power failure.
Parity and ECC
Parity is a method of verifying data integrity. It is used when the reliability of the data is more important than the speed at which it is written or read. Parity adds a bit to each byte so that every byte is an even number. When the data is read or received, the bytes should still be even. If not, the data is corrupt. Parity is used in some network communications, hard drives, and RAM. Error correction code (ECC) detects and fixes corrupt data in RAM. Both Parity and ECC decrease efficiency, but increase reliability.
Motherboards
A motherboard connects everything. It facilitates interoperability among the trinity (CPU, RAM, and motherboard). It communicates with storage devices through SATA and PATA headers. It also allows for expansion through the use of adapter cards. Motherboards usually have integrated I/O ports to support common peripherals.
Best comptia A+ Training, Comptia A+ Certification at Certkingdom.com
BIOS
The BIOS is stored on the CMOS chip that is on the motherboard Comptia A+ Training. The BIOS handles fundamental system configuration. The CMOS chip is actually a combination of NVRAM and volatile RAM. The NVRAM allows the BIOS to be updated (flashed). If the BIOS cannot recognize a new device, updating the BIOS is a solution. A small battery maintains a charge so the settings are not lost in the RAM when the PC is off. If the date and time reset when the computer restarts, replace the battery. The BIOS allows you to do the following:
* Enable/disable integrated devices
* Order the boot sequence
* Manage drive controllers
* Adjust battery and power supply settings
Form Factors
There are a few basic form factors for motherboards. ATX is the basis of all modern motherboards. BTX is slightly bigger and is used primarily by manufacturers. ATX is often the choice of custom-built computers. There are countless motherboard sizes and capabilities. Table 1-3 outlines the common form factors.
Table 1-3 Motherboard Form Factors
Form Factor
Dimensions in Millimeters
Details and Descriptions
ATX
305×244
The basic motherboard.
BTX
325×266
Most PC manufacturers use proprietary versions of the BTX.
Micro ATX
244×244
A smaller square version ATX motherboard with fewer expansion slots.
ITX
215×191
Designed to be small and used with completely integrated devices.
NLX
254×228
Integrated AGP, NIC, and USB support.
LPX
330×229
Expansion cards run parallel to motherboard and can, therefore, fit in to a smaller case.
Expansion Cards and Slots
Expansion cards allow the motherboard to connect and control countless devices to the PC via proxies called adapter cards Comptia A+ Certification. Adapter cards also share some of the processing responsibility, which lightens the load on the CPU. Table 1-4 describes the standard expansion slots.
Table 1-4 Expansion Slots
Adapter Card/Bus Name
Bus Width
Details and Descriptions
PCIe
x1
x4
x8
x16
Full duplex lets data be sent and received simultaneously.
Measured in throughput as a multiple of 250 MBps.
For example, a x4 PCIe slot and card can transfer data at 1000 MBps.
(250 MBps x 4 = 1000 MBps)
PCI
64
32
Current standard, 32 bit and 64 bit, shorter than ISA.
Usually white.
32 bit have two inline slots; 64 bit have three.
AGP
32
Dedicated graphics card slot, 32 bit, shorter than PCI.
Brown.
EISA
32
Old technology, slot 8 and 16 bit versions (32 bit EISA).
ISA
16
8
Black.
Common in older PCs.
Figure 1-2 shows the relative size and form factors of the common expansion slots. You should be able to identify these during your CompTIA A+ Exams.
Figure 1-2
Expansion Slot Comparison
Adapter Cards
The expansion slots support adapter cards. Some cards control internal devices, such as hard drives, and most communicate with external devices, such as monitors, printers, network equipment, and so on. Table 1-5 focuses on the most common adapter cards.
Adapter cards have two connections: One connects to the expansion slot, and the other connects to devices. This usually involves a port or plug. Table 1-5 contains the standard ports.
Table 1-5 Adapter Cards
Adapter
Expansion Buses
Ports and Plugs
Details and Descriptions
NIC
PCI, PCIe, or USB
RJ45
Connects the PC to a network.
Wireless NIC
PCI, PCIe, or USB
2.4 GHz Antenna
Connects a PC to a wireless network.
Video Adapter
PCIe, AGP, or PCI
VGA, DVI, HDMI, Component Video, S-video
Translates data into video signal for the monitor.
USB
PCI
USB
Is an adapter in this case. Like an SCSI, it forwards data onto another kind of bus. It often provides both internal and external USB ports.
IEEE 1394 (FireWire)
PCI or PCIe
FireWire
Is similar to USB, but it is almost twice as fast. Commonly used to transfer video or other data intensive applications.
Sound/Audio Adapter
PCI or PCIe
Mini DIN (TSR 3.5)
Translates data into audio signal for speakers.
SCSI Adapter
PCI or PCIe
Internal SCSI header and often an external SCSI port
Is an additional bus link, like a transfer station. It forwards data to and form the PC to SCSI HDDs and devices.
RAID Adapter
PCI or PCIe
Multiple hard drive connections SATA, PATA, or SCSI
Controls the spreading of data across multiple HDDs. Commonly used for SCSI but can also be used for SATA.
eSATA
PCIe, PCI
eSATA
Connects external SATA drives to the PC.
Modem
PCI or USB
RJ11
Is like a combination NIC and sound adapter. It connects the PC to an audio/telephone based network.
IEEE 1284 (Parallel Port)
PCI
DB25
Connects peripheral parallel devices mainly printers to the PC. The distinctive cable has a 25-pin D plug on the computer end and a 36-pin Centronics port on the other.
-Moves data along multiple channels simultaneously (parallel).
Serial Port
PCI
DA15
Connects peripheral parallel devices to the PC. Not commonly used today. Moves data along one channel, bit by bit (serial).
Daughter Boards and Riser Boards
Daughter boards and riser boards are essentially the same device. These smaller boards plug into the motherboard that expand the number of expansion slots, ports, or, in some cases, add devices. If the board is used solely to add extra PCI slots or turn the angle of adapter cards to fit into smaller cases, it is a riser. The two exceptions are Audio Modem Riser (AMR) and Communications Network Risers (CNR). They are an evolutionary missing link between true integrated devices and full-fledged expansion cards.
Storage Devices
There are many types of storage media: magnetic disk, tape, laser, and solid state flash. There are internal drives and external storage devices. Internal hard drives mount in 3.5 inch or 2.5 inch bays. Optical drives mount in 5.25 inch bays. External drives connect through many kinds of readers and ports. USB, FireWire, and eSATA are common. Card readers and optical drives support flash memory cards and optical discs.
Dynamic and Solid State Drives
Dynamic state drives (DSD) use armatures that move read/write heads over spinning magnetic platters. The disk is organized into tracks (rings) and sectors (radial lines).
Solid state drives (SSD) contain chips that contain NVRAM. This is often called flash memory. The name came from flashing the CMOS Chip’s NVRAM to update the BIOS. Solid state HDs, flash, NVRAM, Thumb drives, Jump drives, and USB drives are essentially the same type of device.
Optical Drives CD/DVD/RW/Blu-Ray
Optical disks organize data in a long outward spiral. Optical drives use a laser to shine on the surface of the spinning disk. The laser reflects off the surface and hits a sensor or hits a bump and bounces somewhere else. From the sensor’s perspective, it “sees” a binary pattern. Table 1-6 compares the different kinds of optical drives.
Table 1-6 Optical Drives
CD Family
DVD Family
Details and Descriptions
CD-ROM
DVD-ROM
Can only read premade disks.
CD-R
DVD+/-R
(Recordable) Write a disk once and it is read only after that.
CD-RW
DVD+/-RW
(Rewritable) Read and write a disk repeatedly.
(CDRAM is not an optical drive)
DVD-RAM
(“Endlessly” rewritable) Used primarily as surveillance camera footage.
Installing SATA, PATA, and SCSI Drives
Serial ATA drives are fast becoming the industry standard. They are hot swappable, and the header must be enabled in the BIOS. eSATA is simply an extension cord that puts a SATA header on the outside of the case for external SATA HDs. To install a SATA drive, simply plug it into a SATA or eSATA header and make sure that header is enabled in the BIOS.
Parallel ATA (PATA) is more complicated. The BIOS manages PATA configurations. There are typically two PATA channels: primary and secondary. Each channel can contain two drives: master and slave. The master/slave or cable select (CS) settings must also be set by jumpers on the drives. The cable select allows the drive at the far end of the cable to be master. Note that, in some cases, in both 80 and 40 pin PATA environments, the CS simply does not work. Simply set the jumpers to reflect the master on the end and slave in the middle. If you still have no luck, consider an HDD failure or PATA controller failure. Put together, any given PATA drive (HDD or optical) has one of the assignments shown in Table 1-7.
Table 1-7 Typical PATA Settings
PATA Designation
Number
Typical Assignment
Jumper Setting
BIOS Setting
Primary Master
0
Main Hard Drive
Master
Auto Detect
Primary Slave
1
(Available)
N/A
None
Secondary Master
2
Main Optical Drive
Master
Auto Detect
Secondary Slave
3
(Available)
N/A
None
SCSI is actually a small network of devices controlled by an SCSI controller. The controller is a card that plugs into a PCI or PCI-e slot and has one of many different kinds of SCSI style ports on the outside and several internal ribbon cable connections. One way to spot an SCSI cable is its width. It will always be the widest (most pins) in the PC, markedly more than PATA 40, FDD 34, and SATA 7. (SATA sometimes has 15 pins if it provides its own power.) Another way SCSI cables differ from other cables is that they have nine connectors to support the card and eight devices. An SCSI array requires unique IDs, created using a binary code: 3 bits for SCSI1 and 4 bits for Wide SCSI. This code is set by jumper, dip switch, push button switch, or can be configured with a separate SCSI BIOS. SCSI arrays also need a common medium (SCSI cable), termination at each, and a controller card.
Just like on a network, every device needs a unique ID number. SCSI “chains” need terminators at each end to absorb the signal. In place of terminators, it is common to install a termination enabled device at each end to serve as both HDD and terminator.
RAID
Redundant Array of Inexpensive (or Independent) Disks (RAID) has several defined levels, but the most common are 0, 1, and 5. RAID 0 writes the data across two drives. This increases speed, but does not provide any protection. Striping is the technique used to write the data across multiple disks. Raid 1 (mirroring) simply copies one HDD to the other.
In RAID 5, there are at least three HDDs. RAID 5 also strips the data so that it has some benefit of increased performance and spreads out the data in case of failure. RAID 5 is the most common implementation. Hybrids such as RAID 1+0 and 0+1 exist, and they require at least four disks, because they are either two striped disks that are mirrors to two others, 0+1, or they are two mirrored disks striped to two others, 1+0.
Table 1-8 compares SATA, PATA, and SCSI drives.
Table 1-8 Drive Interfaces
Interface
Drives per Channel
Number of Pins
Hot Swappable
Descriptions and Details
PATA, ATA, IDE, EIDE
2
40
80
No
Old standard.
Two drives per channel.
Jumpers assign master and slave drives.
SCSI
8 or 16
50
68
80
Yes
Typically found on servers.
Drives are arranged along a bus-like cable with terminators on both ends.
Jumpers or dip switches assign drive numbers in binary.
SATA
1
7 or 15
Yes
Small cable improves air cooling.
Faster than PATA. One drive per channel.
No jumpers, no master, and no slave
FDD
1
34
No
Only for the FDD.
Pin 1 is usually oriented closest to the power connector, but look for the red stripe.
Some old FDD cables support multiple FDDs.
They have a twist in the middle of the ribbon connectors.
Media Cards
There is a wide variety of SSD storage cards used primarily in phones, cameras and other portable devices. PCs use card readers to interface with this type of storage media. The secure digital card (SDcard) is a common media card. One particular note about SDcards is they have a switch that makes the card read/write or read-only. Floppy disks also have this feature. SDcards are small and hold a considerable amount of data that is comparable to small HDs.
Other Storage Devices
Floppy Disk Drives (FDD) mount to a 3.5-inch bay and read a removable media, such as the SDcard. Unlike the small hi-capacity SDcard, the floppy disk is about 3 inches square and holds only 1.44 MB.
USB flash drives are essentially a smaller (both in size and capacity) external SSD that connects through a USB port. These are easily lost and should not be used to store secure information.
Network attached storage (NAS) is an HD with a NIC interface. It often uses a web interface and controls user access. These devices are a small office, home office (SOHO) version of proper file servers found in corporate environments. A mapped drive is an icon that is a shortcut to an NAS or file server.
Cooling
There are several methods of removing heat from a PC. The most common solution is a heat fan that blows air over a heat sink that is held firmly to the CPU. Heat sinks use parallel fins to increase the surface area like motorcycle and lawn mower engines. Many GPUs have their own cooling fan and heat sink assembly.
A thermal compound is used between the heat sink and the CPU. Note: The thermal compound is poisonous and toxic to humans. Use care when applying or removing thermal compound. Dust collects on the heat sink, which decreases its efficiency. Use compressed air or a PC vacuum to remove dust.
In some exotic and gaming PCs, liquid cooling systems transfer heat from the CPU to a radiator using water and antifreeze. These work in much the same way as an automobile’s cooling system. They are somewhat less reliable, but they provide excellent heat exchange.
Power Supplies
Safety first: Do not open a power supply. It contains capacitors that hold a dangerous charge, even while unplugged. It is a field replaceable unit (FRU). In other words, if it is broken, simply replace the entire power supply. Before sending it to a recycling facility, the capacitors should be discharged by touching and connecting the phase with the ground plug and then the neutral to the ground plug with an insulated screwdriver or pliers.
Most power supplies follow a standard form factor. The myriad form factors of computers warrants an equally diverse number of power supply form factors.
Power supplies are measured in watts. The watts output should exceed the PCs power demand. There are four kinds of power connections from the power supply top to the PC. Berg and Molex are the standard small and large (respectively) connections for drives and other devices. The motherboard has a 20-pin connector and most have an additional 4-pin connector.
Power fluctuations are devastating to a PC. Table 1-9 describes five power fluctuations.
Table 1-9 Power Fluctuations
Power Condition
Description
Blackout
Power failure
Brownout
Too little voltage
Sag
Very brief time (milliseconds) of too little voltage
Surge
Too much voltage
Spike
Very brief time (milliseconds) of too much voltage
Table 1-10 describes solutions to the previous power issues.
Table 1-10 Power Protection Devices
Power Protection Device
Description
Surge Protector
Multiple plugs.
Protects against too much voltage.
Note: Power strips and standard multiplugs do not offer such protection.
Line Conditioner
Cleans and smoothes the AC power signal.
Standby Power Supply (SPS)
Backup power supply (usually a battery).
Uninterruptible Power Supply (UPS)
A UPS is usually a battery backup to the computer that is recharged by the wall outlet. UPSs are measured by the volt-amp (VA) rating.
Monitors and Display Metrics
Contrast ratio is the comparison of the brightest to the darkest color a monitor can create. The higher the ratio, the more brightness variation exists in the monitor.
Video cards have a basic resolution, usually 640×480 or 800×600, with 256 colors. If the PC boots to this reduced resolution and limited color scheme, it needs a better video driver. Table 1-11 shows the resolutions you need to know for the A+ exam.
Table 1-11 Monitor Resolutions
Name
X Pixels Wide
Y Pixels Tall
VGA
640
480
SVGA
800
600
XGA
1024
768
XGA+
1152
864
SXGA
1280
1024
SXGA+
1400
1050
UXGA
1600
1200
QXGA
2048
1536
These are examples of 4:3 aspect ratios. Many new computers and laptops use a 16:9 aspect ratio (HDTV/widescreen). After the correct drivers are installed, an LCD screen really should be run in its native mode.
CRT
Warning: Do not open CRTs. They are field replaceable units (FRU). In other words, replace CRT. Do not fix them. They contain capacitors that can shock you long after they are unplugged. Before sending CRTs to a recycler for disposal, the capacitors should be discharged by touching and connecting the phase with the ground plug and then the neutral to the ground plug with an insulated screwdriver or pliers.
A Cathode Ray Tube (CRT) monitor has many manual adjustments that should all be set to “middle” level. A beam sweeps sideways lines down the entire length of the screen 60–100 times a second. The width and height of the picture is controlled by controls Vertical and Horizontal, respectively. Contrast and brightness should also be set for a middle setting. Contrast controls the ratio of the brightest and darkest light. Brightness controls the overall intensity of the display. They are physically measured diagonally. A 17-inch display means it is 17 inches of viewable display measured from diagonal corners. Interlacing draws the odd numbered rows of each frame, and then one-sixtieth of a second later, fills the space with the even numbered rows.
LCD
Liquid Crystal Display (LCD) is quickly replacing large, heavy CRT monitors. LCD monitors are illuminated several different ways: a flat florescent tube, a panel of LEDs, or in the case of LCD projectors, a bright bulb. LED backlighting offers more clarity, thinner, and is more rugged than the florescent.
Passive matrix LCD monitors have chips that control the vertical and horizontal sets of wires. When a pixel is charged by both chips, it turns on. Active matrix monitors act like one big integrated circuit with the crystals for transistors.
Other Display Devices
The two principal measures of projectors are resolution and lumens. A lumen is a measure of brightness. There are two competing display technologies that make projectors and, by extension, rear projection TVs/monitors work. LCD is a small high-definition LCD screen with a light shone through it, like a stained glass window. Digital Light Processing (DLP) uses an array of mirrors that reflected light either onto the screen or away, in much the same way optical drives read their media.
It is not uncommon to have multiple monitors on one PC. The most common case of this is a laptop paired with a projector. Function keys toggle among settings that mirror the display, extend the display from the main screen onto the projector, or run the projector exclusively and shut off the main screen. Workstation and gaming PCs commonly have two or more monitors usually set up as a continuation from one to the next. The display settings in the Control Panel provide more control and support for multiple monitors.
I/O Devices
Most input/output (I/O) devices connect to a PC via a USB port. Even wireless devices ultimately terminate at the PC through a USB port. All I/O devices require drivers. Drivers are instructions to teach the OS how to use and communicate with a new piece of hardware. They are normally stored on CDs that come with the device, but they can also be downloaded from the manufacturer’s website. Often, drivers are included in the OS for commonly used devices, such as mice, keyboards, USB storage, and many printers.
Mice and Keyboards
Optical mice use an LED to illuminate the area directly beneath the mouse and a motion-sensing technology to determine the direction and speed of that surface as the mouse moves. Ball mice use a ball that roles on two rollers mounted perpendicular to each other. One measures movement along the Y axis and the other on the X axis.
Speakers and Microphones
The audio port uses a “headphone jack.” The formal name for this port is a mini DIN Tip Sleeve Ring (TSR) 3.5 millimeter jack. This makes the audio port compatible with standard stereo equipment. A higher quality audio connection splits the signal into component signals. Dolby 5.1 uses five and often seven ports each to a dedicated speaker. These are analog signals, which means that the sound card is responsible for digital-to-audio conversion (DAC). Sony/Phillips Digital Interface Format (SPDIF) sends a digital signal over a fiber-optic line to the speakers where it is decoded and converted to an analog signal and, ultimately, an audible sound.
Microphones are essentially speakers in reverse. The diaphragm moves in response to sound waves. That signal is converted into a digital signal inside the sound card. Note: The pink is a microphone port, the blue color is a line in like a stereo or iPod, and the green color is audio out for speakers and headphones. These are de facto standards and are, therefore, not consistent among all manufactures.
Video Input Devices
Still image, video, and webcams work on the same basic principal. A charged coupled device (CCD) or complementary metal-oxide semiconductor (CMOS) converts a visual input into a binary stream through an analog-to-digital conversion (ADC). A significant difference is the way in which the camera transfers that image to the PC.
With standalone video cameras (camcorders and digital cameras), video and pictures are often stored as files that are transferred to the PC, such as a USB flash drive through a USB, FireWire port, or Bluetooth connection. In streaming video environments (security cameras, TV, and movie production), the ADC can take place in the camera and stream a digital signal through a USB or FireWire port.
In many situations, the camera does not stream a digital signal. Instead, it sends an analog signal through RCA, S-video, network interfaces, or proprietary ports. In this case, the ADC takes place in a video capture card.
Once on the PC, the video must either be stored or viewed in real-time or both. Applications such as video-editing software manipulate the raw video, much like a word processor can open, edit, and save a document.
Other I/O Devices
Some devices require additional applications to work properly. Biometric devices combine an input device with an application that compares a unique pattern retina, fingerprint, palm print, and so on, to a password. That password is then used to gain access to the OS or file. Touch screens are an input device that maps the coordinates of the touch location to an application that translates that into executable commands or files. Barcode readers shine a laser on a black-and-white barcode. The laser reflects the pattern to a sensor and reads the code. That code is compared to a database and the associated item or file is accessed.
Laptop Hardware
There are a few types of laptops, each with a different philosophy. A general laptop (notebook) is a portable, battery-powered desktop. A netbook is a barebones, tough, lightweight notebook that is cheap, but has limited capabilities. An ultra mobile personal computer (UMPC) is powerful, small, and very expensive compared to traditional laptops and netbooks.
Laptop Form Factors
Most components in a laptop are specially designed to reduce weight, space, heat, and power consumption. As a result, many have unique form factors. Small Outline Dual Inline Memory Module (SODIMM) and MicroDIMM are RAM form factors used in laptops and mobile devices (smart phones), respectively. Laptop hard drives measure 2.5 inches and can either be dynamic (platters, read/write heads) or solid state (flash). Optical drives are often removable or purely external and connect through a USB port.
ACPI Power Management
Advanced Configuration Power Interface (ACPI) is found in the power management applet in the Control Panel. On a historical note: Advanced Power Management (APM) is the predecessor of ACPI and was supported in 9x, 2K, XP. Vista and Windows 7 do not support APM. ACPI is not exclusively a laptop technology, but it is designed to maximize battery life. ACPI must first be enabled in the BIOS, like an integrated device. There are six power states, as shown in Table 1-12.
Table 1-12 ACPI Power States
State
CPU
RAM
Description
S0
On
On
PC is fully on.
S1
On
On
Power saving mode.
S2
Off
On
More power saving.
S3
Off
Slow
Standby mode.
S4
Off
Off
Hibernate mode.
S5
Off
Off
PC is fully off.
Batteries
Batteries are a major issue with all portable devices. Physical dimensions and connections vary widely based on the manufacturer. In addition to laptop batteries’ proprietary nature (noninterchangeable), they are also measured by the number of cells and Amps per hour (Ah). A cell is the actual electrochemical unit. Ah is a rough estimate of how many amps are delivered over time.
Over time, the electrochemical reaction happens faster and leads to the battery forming a “memory.” Periodically, technicians “exercise” some batteries to combat memory problems. To exercise a lead-acid, alkaline, and Ni-Cad, drain the electricity completely and then charge it slightly above normal several times in a row. Ni-Mh, Li-Ion, and Li-Po naturally do not have memory problems. All batteries from giant UPS to BIOS must be disposed of according to local government regulations. Table 1-13 describes the characteristics of different battery types.
Table 1-13 Batteries
Battery
Characteristics
Usage
Ni-Cd
Heavy, long life, bad memory.
Power tools, cordless phones, camera flash, motorized toys. Anything that draws a big load and does not live long outside the charger.
Ni-MH
Moderate weight, moderate life expectancy.
Cell phones, GPS systems, digital cameras, flashlights. Most things that are meant to be carried around for a while but don’t have a large electrical load.
Li-Ion
Light, long lasting. It will catch fire if overcharged or too much draw.
Cell phones, laptops, and medical devices like pacemakers and monitors.
Li-Po
Quick recharge, small, light, expensive, medium lasting, medium life span.
PDA, laptops, MP3 players, gaming devices, radio controlled toys.
Laptop I/O Devices
Laptops and portable devices have many unusual I/O methods. Touch pads and touch screens are essentially the same device. A touch screen is clear and sits in front of a monitor. A digitizer is a higher resolution touch screen. Often, it uses a stylus, which is a sharp stick that allows users to contact the screen with precision. This should not be confused with a point stick, which is a pointing device that functions like a small “joystick” game controller in the middle of the keyboard that moves the arrow on the screen. Function keys control many aspects, such as switching between external monitor modes, ten-key pads, and screen settings.
Laptop Expansion
Mini-PCI expansion allows for some additional functionality of laptops. Personal Computer Memory Card International Association (PCMCIA) cards can be used if the laptop is designed for them. Express cards look and act much like PCMCIA cards, but they are slightly narrower. Table 1-14 compares the laptop expansion buses.
Table 1-14 Laptop Expansion Buses
Bus Type
Thickness
Usage and Description
PCMCIA Type I
3.3 mm
SRAM Flash (like a USB flash drive).
PCMCIA Type II
5 mm
Standard PCMCIA, used for Modem, NIC, WiFi.
PCMCIA Type III
10.5 mm
Double thick primarily used as an HDD.
Express Card /34
5 mm
The name notates the length in mm. 34 mm.
Express Card /54
5 mm
-Usually used for card readers and sometimes the cutest little HDD ever made (stick with solid state flash drives).
Printers
There are many kinds of printers. The A+ exam focuses on a few common ones: laser, inkjet, impact (dot-matrix), solid ink, thermal, and dye-sublimation. The following is a list of common printer measurements:
*
Pages per minute (PPM): Measures printer speed.
*
Characters per second (CPS): Measures printer speed in impact (dot-matrix) printers.
*
Dots per inch (DPI): Measures quality (resolution).
*
Mean time between failures (MTBF): Measures reliability.
*
Cost per page (CPP): Measures the price of each printed page. A proper measurement of CPP takes into consideration the cost of ink, paper, electricity, and scheduled printer maintenance.
Laser
Laser printers are good balance between cost and quality. They are quiet, reliable, and produce high quality printouts. Laser printers are not cheap, and toner can be pricy. Except for the initial costs, the actual CPP is low. Table 1-15 outlines the six steps of the laser-printing process with a helpful mnemonic.
Table 1-15 Laser Printing Process
Step
Details of Each Step
Mnemonic
1. Cleaning
The drum is cleaned by a wiper or in some cases an electrical charge can drop excess toner from the drum.
California
2. Conditioning
Puts uniform charge of -600 VDC. This phase is also called charging.
Cows
3. Writing
Laser traces the image on the charged drum and changes the voltage to -100 VDC in those areas the laser touched.
Won’t
4. Developing
Negatively charged toner is applied to the drum and sticks to the areas with altered voltage.
Dance
5. Transferring
The secondary corona wire charges the paper. The toner is statically attracted to the paper.
The
6. Fusing
Rollers melt the toner and embed it into the paper.
Fandango
Another mnemonic that is used to remember the Laser Printing Process: Cool Cowboys Will Drive Their Fords.
Inkjet
Inkjet printers include either thermal or piezoelectric nozzles. Thermal nozzles boil the ink and jets of steamed ink shoot onto the paper. Piezoelectric nozzles energize crystals that vibrate and control ink flow.
Impact Printers
A dot matrix printer uses a group of pins that strike a ribbon against the paper. When the pins are used in combination, they create shapes of letters. Daisy wheel printers have a wheel of letter symbols and numbers that rotate into position, and then the solenoid hits the letter into the ribbon and onto the paper. Impact printers are measured in CPS, not PPM. Near letter quality (NLQ) is the best quality a dot matrix printer can have. Impact printers are used on carbon copy paper because the impact travels through to the carbon copies beneath the original paper.
Solid Ink
Solid ink printers use a combination of laser and inkjet technologies. The solid ink is melted and sprayed (written) to a drum that is transferred onto the paper. These printers are used for posters and other large format, high quality photos.
Dye Sublimation
Dye sublimation is a process that prints the page four times each with a different color of ink. This produces long lasting, high quality images.
Thermal
Thermal printers are used most often on point-of-sale systems, thermal printers print receipts, and other inexpensive continuous feed outputs, such as those produced by EKGs, label makers, and old fax machines. The paper is stored on rolls and is treated so that heat darkens it.
Printer Connections
Regardless of the physical connection, the drivers must be installed on the PC from which the print job is sent. Drivers can be found on the installation CD or on the manufacturer’s website. Printer drivers and printer firmware can be updated based on the manufacturer’s recommendation. The three primary methods to connect to a printer are
*
Directly connected to a PC via USB, parallel, FireWire, or infrared (IR).
*
Directly connected to a remote networked PC that acts as a print server for the network.
*
A networked printer that has a NIC and is a fully capable network device.
USB is the most common method to connect a printer because of the autoconfiguring nature of the USB interface. The entire process is /Parallel (ECC and ECP)/ IrDa.
Local Versus Network Printer
TCP/IP printers are controlled by a print server. Print jobs are sent to the print server, which are forwarded to the printer. A formal print server is a standalone PC with a locally connected printer. Many print servers are integrated into the printer, which eliminates the need for the additional computer and simplifies user management. Print jobs are directed to either uniform (or universal) naming convention (UNC) or an IP addresses. A UNC is always formatted with backslashes, such as \\hostname\sharedfolder\sharedresource.
Printer Maintenance
To improve longevity and reliability, it is important to keep printers clean, supplied, and updated. Note: Always turn off and unplug the printer before cleaning it. Table 1-16 outlines printer maintenance.
Table 1-16 Printer Maintenance
Maintenance
Details
Mnemonic
Clean
Use a vacuum on loose toner and dust.
Use damp cloth for general cleaning. Follow the manufacturers
recommendation for cleaning the rollers
Clients
Supply
Paper.
Ink/toner (all colors).
Seldom
Calibrate
Run printer self checks to align print heads and clean nozzles.
Clearly
Update
Drivers.
Firmware.
Understand
No Comment