A+ Essentials Cram Notes 220-801

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Find A+ Essentials exam cram notes for last minute preparation here:

http://www.simulationexams.com/exam-cram/Aplus-Notes.pdf

The notes is useful for candidates preparing for A+ Essentials as a last minute review of concepts and important points to remember for aplus exam.

Any feedback is welcome.

Vijayb

                                                                  A+ CertNotes

1. Memory
There are basically two important types of RAM (Short for Random Access Memory):
1. SRAM - Static RAM, and
2. DRAM - Dynamic RAM,
SRAM, being expensive, primarily used for Cache memory. DRAM, being cheaper, is used for main
memory. SRAM is widely used for Level 1, Level 2 or Level 3 cache memory. Level 1 cache is
internal to the processor, and level 2 and level 3 caches are external to the processor, it resides on the motherboard.
DRAM: Dynamic RAM holds its data if it is continuously accessed by special logic called a refresh
circuit. If the memory is not refreshed regularly, then the DRAM will lose its contents. This refreshing
action is why the memory is called dynamic.
All PCs use DRAM for their main system memory, instead of SRAM, even though DRAMs are slower
than SRAMs and require the overhead of the refresh circuitry. The reason that DRAMs are used is that they are much cheaper and take up much less space.

Vijayb

RAM is much faster than ROM is, due to the nature of how it stores information. For this reason,
RAM is often used to shadow the BIOS ROM to improve performance when executing BIOS code.
PROM (Programmable ROM) is also a version of ROM and is slower compared to RAM.
The computer main memory usually consists of some type of DRAM. Types of DRAM Packages and
DRAM Memory are explained below:
168 pin DIMM (SDRAM): It can run at much higher clock speeds than conventional memory.
SDRAM actually synchronizes itself with the CPU's bus and is capable of running at 133 MHz and
twice as fast EDO DRAM .
184 pin DIMM (DDR-SDRAM): It supports data transfers on both edges of each clock cycle,
effectively doubling the memory chip's data throughput. DDR-SDRAM is also called SDRAM II.
DDR stands for Double Data Rate.
240 DIMM (DDR2-SDRAM): It supports higher speeds than it's predecessor DDR SDRAM
240 DIMM (DDR3-SDRAM): It supports speeds faster than DDR2 SDRAM.

Vijayb

PC Memory cards:
SIMMs (Single Inline Memory Modules) have 72 pins on each side of the stick. SIMMs are 32 bits
wide, and you need two 72-pin SIMM sticks (Minimum) on a Pentium class computer. This is because
the bus width is 64 bits in a Pentium class computer. Note that each side of each pin on a SIMM stick
is same; where as each side of each pin on a DIMM (Dual Inline Memory Module) has separate signal
flowing.
A DIMM (Dual-Inline Memory Module) has two rows of connecting fingers; one row on each side,
and the total number of contacts is 168 for SDRAM, 184 pins for DDR, 240 pins for DDR2 and DDR3
memories.
144-pin small outline DIMM (soDIMM) is commonly used in notebook computers. 144-pin micro-
DIMM is still smaller than the so-DIMM and used in sub-notebook computers. 72-pin SODIMM was
used in older laptops.
A Secure Digital (SD) card is a small memory card used to make storage portable among various
devices, such as cellular phones, PDAs, digital cameras, music players, and personal computers. It
uses flash memory to provide nonvolatile storage, which means that a power source is not required to retain stored data.

Vijayb

PCMCIA Cards:
1. Type I: 3.3 mm thick. Used for memory upgrade cards.
2. Type II: 5 mm thick. Used for modem and network cards. Some are combination Modem/NIC
cards.
3. Type III: 10.5 mm thick. Used in PC card hard drives.
The two most important features of PCMCIA are its Plug and Play and Hot Swapping capabilities.
The following are usually hot pluggable devices:
a.eSATA (even SATA is hot pluggable under XP and Vista)
b.USB
c.Expresscard/54
But you need to follow proper procedures if you want to remove a USB or eSATA device while the
computer is on. The Personal Computer Memory Card International Association (PCMCIA) developed
the both the ExpressCard standard and the PC card standards. The host device supports both PCI
Express and USB 2.0 connectivity through the ExpressCard slot; cards can be designed to use either mode. The cards are hot-pluggable.

Vijayb

2. Display Adapters and Monitors

Monitor Connectors:

· If you are using a Monochrome / CGA/ EGA monitor, it is a digital monitor and will have a DB-9
Male connector that plugs into a digital adapter.
· If you are using a VGA/ SVGA monitor, it will have a male DB-15 connector that plugs into an
analog adapter. You should never interchange an analog monitor to that of a digital adapter and vice
versa, or severe damage may take place.

Vijayb

Video types:

The table below compares various video types:

Video monitor                         Max. Color depth                            Max. Resolution

CGA                                           16 Colors                                     160X100
EGA                                           64 colors                                      640X350 (Graphics Mode)
VGA                                           256 colors                                    640X480 (Graphics Mode)
SVGA                                         16 Million Colors                           1280X1024 or even more

Vijayb

When you are installing a different SVGA monitor, it is unlikely that the new monitor has the same
capabilities as the old one. As a result, the image on the screen may not be readable. In such instances, change the video resolution to Standard VGA before installing the new monitor. You can change the resolution appropriately after the image on the screen is readable with the new monitor. It may also be necessary to load appropriate device driver, if you are installing a different display adapter.

LCD Monitors:

The 'native resolution' specification points out one of the big differences between LCD and CRT
displays. If you run an LCD at any resolution other than its native resolution, the display will become blurry, especially with text. The reason this happens on LCDs is that they are made up of tiny cells in a matrix (called the native resolution). For instance, if the native resolution is listed as 1280×1024, then there are 1280 cells across and 1024 cells down the screen. If you only display at 1024×768, then a large number of the pixels are being 'stretched' over multiple cells, which is what causes the image quality to degrade.

Vijayb

Various resolutions commonly used with LCD monitors are as given below:

1024 x 768 is XGA (eXtended Graphics Array)
1280x720 is WGA/WXGA (Wide eXtended Graphics Array)
1280 x 1024 is SXGA (Super eXtended Graphics Array)
1400x1050 is SXGA+ (Super eXtended Graphics Array Plus)
1680x1050 is WSXGA (Wide Super eXtended Graphics Array Plus)
1600x1200 is UXGA (Ultra eXtended Graphics Array)
1920x1200 is WUXGA (Wide Ultra eXtended Graphics Array)

Wide screen format aspect ratio is typically 16:10 for computer monitors and 16:9 for LCD
televisions. Aspect ratio of 16:10 conforms with WUXGA standard. Further note that UXGA has a
resolution of 1600X1200 and an aspect ratio of 4:3.

Vijayb

Products or instrumentation equipped with a touch screen normally require a calibration routine upon
power up because it is difficult to perfectly align a touch screens coordinates with those of the display
underneath it. Calibration is necessary when the coordinates of the area touched on the screen are not sufficiently close to the coordinates on the display. Without proper calibration, software may not
respond correctly when a soft button or icon is pressed.It is recommended that you clean the LCD
screen with clean water, using a soft cotton cloth. Do not spray water directly on the screen. First wet
the cloth (no dripping of water), and wipe the LCD screen gently.

Monitors and static charge:

1. Monitors accumulate very high static charges and need to be handled very carefully. Before
attempting any repair, it is important to discharge any accumulated charges on the monitor. You can
use a jumper, one end of which is grounded, and touch the other end of the jumper wire to the anode of the monitor. While doing so, ensure that you are not in direct contact with the jumper wire or the anode. You can use a screwdriver, or a nose pliers with rubber handle for this purpose. A "POP" sound can be heard when the static charges accumulated on the anode lead getting grounded through the jumper wire. Static charges accumulated on monitors may lead to severe burn or even fatal, if come into direct contact.

2. Never wear a wrist strap when working on monitors. Monitors contain very high voltages,
sometimes fatal to human, even when the power is turned off. If you are wearing wrist strap, the
human body works as a conduit to discharge the electric charge.

Vijayb

3. Floppy, CD ROM, Hard Disk

The storage capacity of various types of floppy:

Size                        Type                             Storage

5 1/4"                     DSHD                             1.2MB
3 1/2"                     DSDD                             720KB
3 1/2"                     DSHD                             1.44MB
3 1/2"                     DSED                             2.88MB

A floppy cable will have 34 wires, and the wire with red stripe signifies wire going to pin number 1 of the connector.

The floppy ribbon cable is distinguished easily from that of an IDE cable by a small twist in the cable. The purpose of the twist is to differentiate between floppy drive A and floppy drive B

Vijayb

Characteristics of a floppy drive:

1. The ribbon cable connecting the floppy drive to the motherboard is 34 wires wide.
2. There can be a maximum of two floppy drives in a PC

When you have two hard disk drives, the following two combinations are possible:

1. Install the drives one each on primary and secondary controllers and designate both as Masters.
2. Install both the drives on the primary controller and designate one as Master and the other as Slave.

CD-R stands for CD- Recordable. You can record data onto a CD-R only once. CD-RW stands for
CD-ReWritable, and as the name suggests, you can record data any number of times onto a CD-RW
(subject to wear and tear). CD-R is represented by two speeds (AxB), the former is the write speed and the latter is the read speed. The read speed is always higher than the write speed. Some typical CD-R

speeds are as given below:

4X24,
8X32,
16X32 etc.

DVD, also known as Digital Versatile Disc or Digital Video Disc, is an optical disc storage media
format. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs (CDs), but store more than six times as much data.

Vijayb

DVD comes in single layer (SL) or dual layer (DL). They are also distinguished as single sided (SS) or
double sided (DS). There are four possible combinations:

DVD-S (12 cm, SS/SL): 4.37 GB capacity
DVD-9 (12 cm, SS/DL): 7.95 GB capacity
DVD-10 (12 cm, DS/SL): 8.74GB capacity
DVD-18 (12 cm, DS/DL): 15.90GB capacity.

Further, DVD-S stores about two hours of video, where as DVD-18 can store up to eight hours of
video.

MS –DEFRAG utility:

To defragment the hard disk, you can run Microsoft defragment utility by issuing a command
"DEFRAG".

Vijayb

4. CPU

Processor package types:

· 8088, 8086 processors used 40 pin DIPs. 80286,80386, 80486, and some Pentium computers
(60MHz, 66MHz) used PGA (Pin Grid Array).
· Pentium chips (75 MHz and above) used SPGA (Staggered PGA). Pentium II CPUs use catridge type
mounting method, called "slot-1".

CPUs and features:

Processor                  Socket type                        Register                 Data Bus             Address bus

8088                          DIP                                     16 bit                       8 bit                      20 bit
80286                        LLC/PGA/PLCC                    16 bit                      16 bit                     24 bit
80386SX                    PGA                                     32 bit                      16 bit                    24 bit
80386DX                    PGA                                     32 bit                      32 bit                    32 bit
80486SX                    PGA                                     32 bit                       32 bit                   32 bit
80486DX                    PGA/SQFP                           32 bit                       32 bit                    32 bit
Pentium                     Socket 5 SPGA/
                                   Socket 7 SPGA.                   64 bit                       64 bit                   32 bit
Pentium Pro               Socket 8 SPGA                     64 bit                       64 bit                   32 bit
Pentium II                  SEC Slot 1
Pentium III                 SECC-2 / PPGA or
                                     FC-PGA
Pentium IV                 socket 423/socket 478/
                                   socket 775                            64                           64                       36 bit*
Pentium Dual Core     Socket 775 (LGA775)             64                           64                       64 bit*
Pentium Quad Core    Socket 775 (LGA775)            64                           64                        64 bit*

Vijayb

* 32-bit operating systems like Windows XP can support only 32 bits of addressing space, and hence only 4GB of memory can be used. By using 64-bit operating systems, 16 Exa bytes (EB) of RAM can be used. 36 bits of address space can access up to 64GB of memory.

CPU models 80486SX, and above contain on board cache memory.

Address Bus Size                                  Maximum RAM

    32 bits                                                  4GB
    36 bits                                                  64GB
    40 bits                                                  1TB.
    44 bits                                                  16TB
    64 bits                                                  16 EB (Exa Bytes)