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CHAPTER 3
MEMORY STORAGE
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Storage Memory
Computer data storage, often called storageormemory, refers to computer components,devices, and recording media that retain digitaldata used for computing for some interval of
time. Computer data storage provides one of the core
functions of the modern computer, that ofinformation retention. It is one of thefundamental components of all moderncomputers, and coupled with a centralprocessing unit (CPU, a processor), implementsthe basic computer model used since the 1940s.
Source : http://en.wikipedia.org/wiki/Computer_data_storage
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Purpose of Storage
A digital computerrepresents data using the binary numeral system.Text, numbers, pictures, audio, and nearly any other form ofinformation can be converted into a string ofbits, or binary digits,each of which has a value of 1 or 0.
A piece of information can be handled by any computer whosestorage space is large enough to accommodate the binaryrepresentation of the piece of information, or simply data.
Without a significant amount of memory, a computer would merelybe able to perform fixed operations and immediately output the
result. store operating instructions and data.
http://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Binary_numeral_systemhttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Data_(computing)http://en.wikipedia.org/wiki/Instruction_(computer_science)http://en.wikipedia.org/wiki/Instruction_(computer_science)http://en.wikipedia.org/wiki/Data_(computing)http://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Binary_numeral_systemhttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Computer -
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Generally, the lower astorage is in thehierarchy, the lesser itsbandwidth and thegreater its access latency
is from the CPU. Thistraditional division ofstorage to primary,secondary, tertiary andoff-line storage is also
guided by cost per bit. Type of storage memory : Primary storage Secondary storage Off-line storage
Tertiary storage
http://en.wikipedia.org/wiki/Bandwidth_(computing)http://en.wikipedia.org/wiki/Latency_(engineering)http://en.wikipedia.org/wiki/Latency_(engineering)http://en.wikipedia.org/wiki/Bandwidth_(computing) -
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Secondary storage
Secondary storage (orexternal memory) differs fromprimary storage in that it is not directly accessible by theCPU.
computer usually uses its input/output channels toaccess secondary storage and transfers the desired datausing intermediate area in primary storage.
Secondary storage does not lose the data when thedevice is powered downit is non-volatile.
Example: Rotating magnetic storage - hard disk drives optical storage CD,DVD flash memory - USB flash drives floppy disks, magnetic tape,
http://en.wikipedia.org/wiki/Input/outputhttp://en.wikipedia.org/wiki/Data_bufferhttp://en.wikipedia.org/wiki/Hard_disk_drivehttp://en.wikipedia.org/wiki/Optical_disc_drivehttp://en.wikipedia.org/wiki/Flash_memoryhttp://en.wikipedia.org/wiki/USB_flash_drivehttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/Magnetic_tape_data_storagehttp://en.wikipedia.org/wiki/Magnetic_tape_data_storagehttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/USB_flash_drivehttp://en.wikipedia.org/wiki/Flash_memoryhttp://en.wikipedia.org/wiki/Optical_disc_drivehttp://en.wikipedia.org/wiki/Hard_disk_drivehttp://en.wikipedia.org/wiki/Data_bufferhttp://en.wikipedia.org/wiki/Input/output -
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Tertiary storage
Tertiary storage ortertiary memory,[3] provides a third level ofstorage. Typically it involves a robotic mechanism which will mount(insert) and dismountremovable mass storage media into a storagedevice according to the system's demands.
Useful for extraordinarily large data stores, accessed without humanoperators.
Example : tape libraries optical jukeboxes.
When a computer needs to read information from the tertiarystorage, it will first consult a catalog database to determine which
tape or disc contains the information. Next, the computer will instructa robotic arm to fetch the medium and place it in a drive. When thecomputer has finished reading the information, the robotic arm willreturn the medium to its place in the library.
http://en.wikipedia.org/wiki/Tape_libraryhttp://en.wikipedia.org/wiki/Optical_jukeboxhttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/Industrial_robothttp://en.wikipedia.org/wiki/Industrial_robothttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/Optical_jukeboxhttp://en.wikipedia.org/wiki/Tape_library -
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Off-line storage
Off-line storage, also known as disconnectedstorage, is a computer data storage on amedium or a device that is not under the controlof a processing unit.
The medium is recorded, usually in a secondaryor tertiary storage device, and then physicallyremoved or disconnected. It must be inserted orconnected by a human operator before acomputer can access it again. Unlike tertiarystorage, it cannot be accessed without humaninteraction.
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Differentiate Secondary Memory
magnetic disk
Magnetic disk: Diskette and Hardisk
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Hard Disk
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Hard Disk Overview A hard disk uses round, flat disks calledplatters, coated on both sides with a
special media material designed to store information in the form of magnetic
patterns.
The platters are mounted by cutting a hole in the center and stacking them
onto a spindle.
The platters rotate at high speed, driven by a special spindle motor
connected to the spindle. Special electromagnetic read/write devices called heads are mounted onto
sliders and used to either record information onto the disk or read
information from it. The sliders are mounted onto arms, all of which are
mechanically connected into a single assembly and positioned over the
surface of the disk by a device called an actuator.
A logic boardcontrols the activity of the other components and
communicates with the rest of the PC.
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Hard Disk
Each surface of each platter on the disk can hold tens of billions ofindividual bits of data.
Each platter has two heads, one on the top of the platter and one on
the bottom, so a hard disk with three platters (normally) has six
surfaces and six total heads.
Each platter has its information recorded in concentric circles calledtracks.
Each track is further broken down into smaller pieces called sectors,
each of which holds 512 bytes of information.
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Hard Disk Platters and Media
Every hard disk contains one or more flat disks that are used toactually hold the data in the drive.
These disks are calledplatters (sometimes also "disks" or "discs").
They are composed of two main substances:
a substrate material that forms the bulk of the platter and gives it structure
and rigidity,
a magnetic media coatingwhich actually holds the magnetic impulses that
represent the data.
Hard disks get their name from the rigidity of the platters used, as
compared to floppy disks and other media which use flexible "platters"
(actually, they aren't usually even called platters when the material is
flexible.)
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Hard Disk Platters and Media
Hard Disk Cylinder
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Hard Disk Platters and Media
The size of the platters in the hard disk is the primary determinant ofits overall physical dimensions, also generally called the drive's form
factor.
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Hard Disk Tracks and Sectors Each platter is broken into tracks--tens of thousands of them--which are
tightly-packed concentric circles.
Trackis one of the many concentric circles that holds data on a disk surface.
A track holds too much information to be suitable as the smallest unit of
storage on a disk, so each one is further broken down into sectors.
A sectoris normally the smallest individually-addressable unit of information
stored on a hard disk, and normally holds 512 bytes of information.
The first PC hard disks typically held 17 sectors per track.
Today's hard disks can have thousands of sectors in a single track, and
make use ofzoned recording to allow more sectors on the larger outer
tracks of the disk.
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Hard Disk Tracks and Sectors
A platter from a 5.25" hard disk, with 20 concentric tracks drawnover the surface. This is far lower than the density of even the oldest
hard disks; even if visible, the tracks on a modern hard disk would
require high magnification to resolve. Each track is divided into
16 imaginary sectors. Older hard disks had the same number of
sectors per track, but new ones use zoned recording with a different
number of sectors per track in different zones of tracks.
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Hard Disk Read & Write Head
The read/write heads of the hard disk are the interface between the
magnetic physical media on which the data is stored and the
electronic components that make up the rest of the hard disk (and
the PC).
The heads do the work of converting bits to magnetic pulses andstoring them on the platters, and then reversing the process when
the data needs to be read back.
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Hard Disk Read/Write Operation Older, conventional (ferrite, metal-in-gap and thin film) hard disk
heads work by making use of the two main principles of
electromagnetic force.
Write : applying an electrical current through a coil produces a magnetic
field;. The direction of the magnetic field produced depends on the
direction that the current is flowing through the coil.
Read : that applying a magnetic field to a coil will cause an electrical
current to flow; this is used when reading back the previously written
information.
Newer (MR and GMR) heads don't use the induced current in the
coil to read back the information; they function instead by using the
principle ofmagnetoresistance, where certain materials change theirresistance when subjected to different magnetic fields.
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Hard Disk An MR head employs a special conductive material that changes its resistance in
the presence of a magnetic field. As the head passes over the surface of thedisk, this material changes resistance as the magnetic fields change
corresponding to the stored patterns on the disk. A sensor is used to detect these
changes in resistance, which allows the bits on the platter to be read.
MR technology is used for reading the disk only. For writing, a separate standard
thin-film head is used. This splitting of chores into one head for reading and
another for writing has additional advantages. Ferrite vs MR Head
The use of MR heads allows much higher areal densities to be used on the
platters than is possible with older designs, greatly increasing the storage
capacity and (to a lesser extent) the speed of the drive.
allows the use of weaker written signals, which lets the bits be spaced closer
together without interfering with each other, improving capacity by a largeamount.
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Hard Disk
Extreme closeup view of a ferrite
read/write head. The head is at the end of
the slider, wrapped with the coil that
magnetizes it for writing, or is
magnetized during a read.
Closeup view of an MR head assembly.
Note that the separate
copper lead wire of older head designsis gone, replaced by thin
circuit-board-like traces. The slider is
smaller and has a distinctive shape.
The actual head is too small to be seen
without a microscope.
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IDE/EIDE CONCEPT
Overview The interface used to connect hard disk and optical drives to a modern PC
is typically called IDE (Integrated Drive Electronics) or the true name is of
this interface is ATA (AT Attachment).
IDE variation :
There have been four main types of IDE interfaces based on three busstandards:
Serial AT Attachment (SATA)
Parallel AT Attachment (ATA, based on the 16-bit AT-bus, also called ISA)
XT IDE (based on 8-bit ISA, obsolete)
MCA IDE (based on 16-bit Micro Channel, obsolete)
Only the parallel and Serial ATA version are used today.
ATA and Serial ATA have evolved with newer, faster and more
powerful versions.
Continue
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IDE/EIDE CONCEPT The newer versions of parallel ATA are referred to as ATA-2 and higher.
They are also called EIDE (Enhanced IDE), Fast-ATA, Ultra-ATA or Ultra-DMA.
ATA-1
ATA-2 (also called Fast-ATA, Fast-ATA-2, or EIDE)
ATA-3
ATA-4 (Ultra-ATA/33)
ATA-5 (Ultra-ATA/66)
ATA-6 (Ultra-ATA/100)
ATA-7 (Ultra-ATA/133 or Serial ATA)
SATA-8 (Serial ATA II)
Even though parallel ATA has hit the end of the of the evolutionary road with
ATA-7, Serial ATA picks up where parallel ATA leaves off and offers greater
performance, higher reliability, easier installation, low cost and establishedroadmap for future upgrades.
Continue
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ATA-1 (AT Attachment Interface for Disk Drives)
Original ATA
Integrated bus interface between disk drives and host
systems based on the ISA (ATA) bus.
Major features: 40/44-pin connectors and cabling
Master/Slave or cable select drive configuration options.
Signal timing for basic Programmed I/O (PIO) and Direct Memory Access
(DMA) modes.
Cylinder, head, sector (CHS) and logical block address (LBA) drive
parameter translations supporting drive capacities up to 228-220(267,386,880) sectors or 136.9GB.
ATA-1 had been in use since 1986 that has BIOS limitation
that stopped at 528MB.
IDE/EIDE CONCEPT
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ATA-2 (AT Attachment Interface with Extensions-2)
Upgraded from original ATA.
First used in 1993.
Major features added to ATA-2 compared to the original ATA
standard include: Faster PIO and DMA transfer modes
Support for power management
Support for removable devices.
PCMCIA (PC Card) device support.
Identify Drive command that reports more information.
Define standard CHS/LBA translation methods for drives up to 8.4GB incapacity.
ATA-2 also known as fast-ATA or fast-ATA-2
(Seagate/Quantum) and EIDE (Western Digital)
IDE/EIDE CONCEPT
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ATA-3 (AT Attachment Interface-3).
First appearing in 1995.
Has minor revision to the ATA-2 standard
Most major changes included the following: Eliminated single-word (8-bit) DMA transfer protocols)
Added SMART (Self-Monitoring, Analysis and Reporting Technology)support for prediction of device performance degradation.
LBA mode support was made mandatory (previously it had been optional)
Added ATA Security mode, allowing password protection for device
access.
Recommendation for source and receiver bus termination to solve noise
issues at higher transfer speeds. SMART enable a drive to keep track of problems that might
result in a failure and therefore avoid data loss.
IDE/EIDE CONCEPT
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ATA/ATAPI-4 (At Attachment with Packet Interface
Extension-4) First appearance in 1996.
ATA-4 included several important additions to the standard included :
Packet Command feature known as the AT Attachment Packet Interface (ATAPI) which
allowed devices such as CD-ROM and CD-RW drives, LS-120 SuperDisk floppy drives,
ZIP drives, tape drive and other types of storage devices to be attached through a
common interface.
The major revisions added in ATA-4 were as follows:
Ultra-DMA (UDMA) transfer modes up to Mode 2, which is 33MBps (called UDMA/33 or
Ultra-ATA/33)
Integral ATAPI support.
Advanced power management support.
Defined an optional 80-conductor, 40-pin cable for improved noise resistance.
Host protected area (HPA) support.
Compact Flash Adapter (CFA) support
Introduced enhanced BIOS support for drive over 9.4ZB (zettabytes or trillion gigabytes)
in size (even though ATA was still limited to 136.9GB)
IDE/EIDE CONCEPT
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ATA/ATAPI-5 (At Attachment with Packet Interface-5) First appear in 1998.
Built on previous ATA-4 interface.
ATA-5 includes Ultra-ATA/66 (also called Ultra-DMA or UDMA/66) which double the Ultra-
ATA burst transfer rate by reducing setup times and increasing the clock rate.
The faster clock rate increases interference, which causes problem with the standard 40-
pin cable used by ATA and Ultra-ATA. To eliminate noise and interference, the newer 40-
pin 80-conductor cable has now been made mandatory for drives running in UDMA/66 or
faster modes. This cable hash 40 additional ground lines between each of the line.
Major additions in the ATA-5 standard include the following:
Ultra-DMA (UDMA) transfer modes up to Mode 4, which is 66MBps (called UDMA/66 or Ultra-
DMA/66)
80 conductor cable
Added automatic detection of 40- or 80-conductor cables.
UDMA modes faster than UDMA/33 are enabled only if an 80-conductor cable is deteched.
IDE/EIDE CONCEPT
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ATA/ATAPI-6 (At Attachment with Packet Interface-6)
Developed during 2000.
Includes Ultra-ATA/100 (also called Ultra-DMA or UDMA/100).
Increase the Ultra-ATA burst transfer rate by reducing setup times
and increasing the clock rate.
Use 80-conductor cable. Major changes or additions in the standard include the following:
Ultra-DMA (UDMA) Mode 5 added, which allows 100MBps (called UDMA/100,
Ultra-ATA/100, or just ATA/100) transfers.
Sector count per command increased from 8-bits (256 sectors 131KB) to 16-bits
(65,536 sectors or 33.5MB) allowing larger files to be transferred more efficiently.
LBA addressing extended form 228 to 248 (281,474,976,710,656) sectors
supporting drives up to 144.12PB(petabytes). This feature is often referred to as
48-bit LBA or greater than 137GB support vendor.
CHS addressing made obsolete; drive must be use 28-bit or 48-bit LBA addressing
only.
IDE/EIDE CONCEPT
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ATA/ATAPI-7 (At Attachment with Packet Interface-7)
ATA-7 began late in 2001.
Major changes or additions in the standard include the following:
Upgrade to UDMA Mode 6 that allows for data transfer up to 133MBps.
Also required the use of an 80-conductor cable.
Inclusion of the Serial ATA 1.0 that makes SATA an official part of ATAstandard.
ATA-7 is last revision of the venerable parallel ATA standard. ATA is
evolving into Serial ATA which was incorporated into the ATA-7
specification.
IDE/EIDE CONCEPT
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SATA/ATAPI-8
SATA/ATA-8 began in 2004 which is a new ATA standard based on
ATA-7 that carry forward the development of Serial ATA while
removing parallel ATA from the standard entireky.
Main features of SATA-8 include :
The removal of parallel ATA from the standard The replacement of read long/write long functions.
Improve HPA management.
IDE/EIDE CONCEPT
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ATA Timeline
PRESENT
ATA-1
ATA-2
ATA-3
ATA-4
ATA-5
ATA-6
ATA-7
SATA
Drive support up to
136.9GB;BIOS issues
not addressed
Faster PIO modes;
CHS/LBA BIOS
translation defined up to
8.4GB;PC-Card
SMART; improved
signal integrity; LBA
support mandatory;
eliminated single-word
DMA modes
Ultra-DMA
modes; ATAPI
Packet
Interface; BIOS
support up to
136.9GB
Faster UDMA
modes; 80-pin
cable
autodetectiopn
100MBps UDMA mode;
extended drive and
BIOS support up to
144PB.
133MBps
UDMA mode;
Serial ATA
Serial ATA II
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HARD DISK DRIVE TROUBLESHOOTING
AND REPAIRING If a hard drive has a mechanical problem inside the
sealed head disk assembly (HAD), repairing the drive is
usually unfeasible.
If the failure is in the logic board, that board can be
replaced with one from a donor drive.
Most hard disk drive problems are not mechanical
hardware problems; instead, they are soft problems
that can be solved by a new LLF and defect-mapping
session.
Soft problems are characterized by a drive that soundsnormal but produces various read and write errors.
Continue
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HARD DISK DRIVE
TROUBLESHOOTING AND
REPAIRING Hard problems are mechanical, such as when the drivesounds as though it contains loose marbles. Constantscraping and grinding noises from the drive, with no readingor writing capability also qualify as hard errors.
In these cases, an LLF is unlikely to put the drive back into
service. If hardware problem is indicated, first replace the logic-boardassembly. You can make this repair yourself and ifsuccessful, you can recover the data from the drive.
If replacing the logic assembly does not solve the problem,contact the manufacturer or a specialized repair shop.
Continue
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HARD DISK DRIVE
TROUBLESHOOTING AND
REPAIRINGTesting a drive When accessing a drive, determine whether the drive
has been partitioned and formatted properly. Procedure :
1. Attach the drive to your system.2. Detecting the drive in the BIOS and saving the changes,
start your operating system from the boot disk.
3. Then from the A: prompt, enter the following command:
4. This produces one of the following responses:DIR C:
Continue
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HARD DISK DRIVE
TROUBLESHOOTING AND
REPAIRINGInvalid drive specification.
Problem: This indicate the drive does not have a valid partition (create by
FDISK) or that the existing Master Boot Record or partition tables
have been damaged. No matter what, the drive must be partitionedand formatted before use. You also get this warning on FAT32 orNTFS partitioned drive if you use a Windows 95 (original version) orMS-DOS boot disk when checking.
Solution: Use a Windows 95B, Windows 98/Me, or Windows 2000 boot disk
to avoid this false massage from FAT32 partitions. Or, use a windows NT, Windows 2000 or Windows XP boot disk todetect NTFS partitions.
HARD DISK DRIVE
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HARD DISK DRIVE
TROUBLESHOOTING AND
REPAIRINGInvalid Media Type.
Problem:
This drive has been partitioned but not FORMATed, or the
format has been corrupted.
Solution:
You should use FDISKs #4 option to examine the drives
existing partitions and either delete them and create new ones
or keep the existing partitions and run FORMAT on each drive
letter.
HARD DISK DRIVE
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HARD DISK DRIVE
TROUBLESHOOTING AND
REPAIRINGDirectory of C:
Problem:
The contents of the C: drive are listed, indicating thedrive was stored with a valid FDISK and FORMAT
structure and data.
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COMPACT DISK
A Compact Disc (also known as a CD) is an
optical disc used to store digital data.
It was originally developed to store sound
recordings exclusively, but later it also allowedthe preservation of other types of data.
Audio CDs have been commercially available
since October 1982. In 2010, they remain the
standard physical storage medium for audio.
Source : http://en.wikipedia.org/wiki/Compact_Disc
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Standard CDs have a diameter of 120 mm and can holdup to 80 minutes of uncompressed audio (700 MB ofdata).
The Mini CD has various diameters ranging from 60 to
80 mm; they are sometimes used for CD singles ordevice drivers, storing up to 24 minutes of audio.
The technology was eventually adapted and expanded toencompass data storage CD-ROM, write-once audio anddata storage CD-R, rewritable media CD-RW, Video
Compact Discs (VCD), Super Video Compact Discs(SVCD), PhotoCD, PictureCD, CD-i, and Enhanced CD.
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A CD is a fairly simple piece of plastic, about four one-hundredths (4/100) of an
inch (1.2 mm) thick. Most of a CD consists of an injection-molded piece of
clear polycarbonate plastic. During manufacturing, this plastic is impressed
with microscopic bumps arranged as a single, continuous, extremely long spiraltrack of data. We'll return to the bumps in a moment. Once the clear piece of
polycarbonate is formed, a thin, reflective aluminum layer is sputtered onto the
disc, covering the bumps. Then a thin acrylic layer is sprayed over the
aluminum to protect it. The label is then printed onto the acrylic. A cross section
of a complete CD (not to scale) looks like this:
Cross-section of a CD
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How do CD-RWs rewriteable CDs
work?Normal CD Normal CD uses microscopic bumps to store data. The surface of the CD contains one long spiral track of data. Along
the track, there are flat reflective areas and non-reflective bumps. The surface of the CD is a mirror, and the bumps disrupt the mirror's
perfect surface. A flat reflective area represents a binary 1, while a non-reflectivebump represents a binary 0.
The CD drive shines a laser at the surface of the CD and can detectthe reflective areas and the bumps by the amount of laser light theyreflect. The drive converts the reflections into 1s and 0s to readdigital data from the disc.
The bumps on a CD are molded into the plastic when it ismanufactured, so they are permanent.
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How do CD-RWs rewriteable CDs
work?
CD-R
There are no bumps on a CD-R.
A clear dye layercovers the CD's mirror.
A write laserheats up the dye layer enough tomake it opaque.
The read laserin a CD player senses the
difference between clear dye and opaque dyethe same way it senses bumps -- it picks up on
the difference in reflectivity.
C C
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How do CD-RWs rewriteable CDs
work?
CD-RW Dye layer can be changed back and forth
between opaque and transparent. The material has the property that it can change
its transparency depending on temperature. Heated to one temperature, the material cools to
a transparent state; heated to anothertemperature, it cools to a cloudy state. By
changing the power (and therefore thetemperature) of the writing laser, the data on theCD can be changed, or "rewritten."
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CD-ROM Standard There are several formats used for data stored on compact discs,
known collectively as the Rainbow Books. The Rainbow Books are a collection of standards defining theallowed formats of Compact Discs.
Red Book CD-DA Digital Audio extended by CD-Text,
Yellow Book
CD-ROM Read-Only Memoryand CD-ROM XA, -An extension to Yellow Book
Orange Book CD-MO Magneto-Optical CD-R alias CD-WO or CD-WORM Recordable, Write Once orWrite
Once, Read Many
CD-RW alias CD-E ReWritable orErasable, The orange book standard references the fact that "Yellow" and "Red"
mix to orange; which means that CD-R and CD-RW is capable of musicand data; although other colors (other CD standards) that do not mix arecapable of being burned onto the physical medium. Orange book alsointroduced the standard for multisession writing.
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White Book VCD Video and Hybrid discs, e.g. CD-Ready, SVCD Super Video,
Blue Book E-CD Enhanced,
CD+ -plus and
CD+G plus Graphics (karaoke) extended by CD+EG / CD+XG,
Beige Book PCD Photo
Green Book CD-i interactive,
Purple Book
DDCD Double Density, Scarlet Book
SACD Super Audio.
Black Book
No rainbow book was applied to the popularDVD and Blu-ray formats.
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What is ISO 9660?
The ISO 9660 standard was introduced in 1988 and is the most widely usedfile format for data (CD-ROM) discs.
ISO 9660 defines a common logical format for files and directories so discswritten to ISO 9660 specifications can be read by a wide array of computeroperating systems (MS-DOS, Windows, Mac OS, UNIX, etc.) as well asconsumer electronics devices.
Due to the vast differences which exist among native file systems ISO 9660takes a lowest common denominator approach resulting in a variety ofrestrictions upon the nature and attributes of files and directories.
Three levels of interchange define these restrictions with level one being themost constraining and level three is the least (at the cost of compatibilitywith some operating systems).
Various protocols are available to extend ISO 9660 to accommodate file
system features specific to individual operating systems (longer file names,deeper directory structures, more character types, etc.) while preservingISO 9660 compatibility with other platforms. These protocols include Joliet(Windows 95 and higher), Apple Extensions (Mac OS) and Rock Ridge(UNIX).
CD ERROR CORRECTION
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CD ERROR CORRECTION
SYSTEM CD technology has built-in error correction systems
which are able to suppress most of the error that arisefrom physical particles on the surface of a disc.
Every CD-ROM drive and CD player in the world usesCross Interleaved Reed Solomon Code (CIRC) detection
and the CD-ROM standard provides a second level ofcorrection via the Layered Error Correction Codealgorithm.
With CIRC, an encoder adds two dimensional parityinformation, to correct errors, and also interleaves the
data on the disc to protect from burst errors. It is capable of correcting error bursts up to 3,500 bits
(2.4 mm in length) and compensates for error bursts upto 12,000 bits (8.5 mm) such as caused by minorscratches.
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CD-ROM TROUBLESHOOTINGMy CD-ROM/DVD drive doesnt work
CD and DVD drives are some of the more failure-prone components in a PC. It is not uncommon for one tosuddenly fail after a year or so of use.
Solution If you having problems with a drive that was newly installed, check the installation and configuration of the
drive.
Check the jumper settings on the drive. If youre using an 80-conductor cable, the drive should be jumped to
Cable Select; if you are using a 40-conductor cable, the drive should be set to either master or slave(depending on whether it is the only drive on the cable).
Check the cable to ensure that it is not nicked or cut and is the maximum of 18 long (the maximum allowed
by the ATA specification).
Replace the cable with a new one or a known-good spare, preferably using an 80-conductor cable.
Make sure the drive power is connected, and verify that power is available at the connector using a digital
multimeter.
Make sure the BIOS Setup is set properly for the drive and verify that the drive is detected during the bootprocess.
Try replacing the drive and, if necessary the motherboard.
If the drive had already been installed and was working before, first read the different discs, preferably
commercial-stamped discs rather than writable or rewriteable ones. Then try the step listed previously.