e5164 Chapter-3-memory-Storage

7/30/2019 e5164 Chapter-3-memory-Storage

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Chapter 3STORAGE MEMORY

Computer data storage , often called storage or memory ,refers to computer components, devices, and recordingmedia that retain digital data used for computing for someinterval of time .

Computer data storage provides one of the core functionsof the modern computer, that of information retention. It isone of the fundamental components of all modern

computers, and coupled with a central processing unit(CPU, a processor), implements the basic computer modelused since the 1940s.


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Purpose of Storage A digital computer represents data using the binary numeral system .Text, numbers, pictures, audio, and nearly any other form of information can be converted into a string of bits , or binary digits, eachof 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 binary representation 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 theresult .

store operating instructions and data .


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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 of storage 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


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Primary Storage Primary storage (or main memory or internal

memory ), often referred to simply as memory , is theonly one directly accessible to the CPU .

The CPU continuously reads instructions stored thereand executes them as required . Any data activelyoperated on is also stored there in uniform manner.

As shown in the diagram, traditionally there are two moresub-layers of the primary storage, besides main large-capacity RAM: Processor registers are located inside the processor . Processor cache is an intermediate stage between ultra-fast

registers and much slower main memory .


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Secondary storage Secondary storage (or external memory ) differs from

primary 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 down it is non-volatile .

Example: Rotating magnetic storage - hard disk drives optical storage CD,DVD flash memory - USB flash drives floppy disks , magnetic tape ,


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Tertiary storageTertiary storage or tertiary memory , provides a third level of storage . Typically it involves a robotic mechanism which will mount (insert) and dismount removable mass storage media into a storage

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.

device according to the system's demands.Useful for extraordinarily large data stores, accessed without humanoperators .Example :


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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 or connected 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 OPERATION A hard disk is a sealed unit that a PC uses for nonvolatile data

storage. The hard drive is used to store crucial programming and data. A hard disk drive contains rigid, disk-shaped platters, usually

constructed of aluminum or glass .


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Hard Disk


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Hard Disk Overview A hard disk uses round, flat disks called platters , coated on both sides with a

special media material designed to store information in the form of magneticpatterns .

The platters are mounted by cutting a hole in the center and stacking themonto 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 ontosliders and used to either record information onto the disk or readinformation from it . The sliders are mounted onto arms , all of which aremechanically connected into a single assembly and positioned over thesurface of the disk by a device called an actuator .

A logic board controls the activity of the other components andcommunicates 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 of individual 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 sixsurfaces 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 to

actually hold the data in the drive. These disks are called platters (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 structureand rigidity,

a magnetic media coating which actually holds the magnetic impulses thatrepresent the data.

Hard disks get their name from the rigidity of the platters used, ascompared to floppy disks and other media which use flexible "platters"(actually, they aren't usually even called platters when the material isflexible.)


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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 of its 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. Track is 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 sector is 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 of zoned 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 oldesthard disks; even if visible, the tracks on a modern hard disk would

require high magnification to resolve. Each track is divided into16 imaginary sectors. Older hard disks had the same number of

sectors per track, but new ones use zoned recording with a differentnumber 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 themagnetic physical media on which the data is stored and theelectronic components that make up the rest of the hard disk (andthe PC) .

The heads do the work of converting bits to magnetic pulses andstoring them on the platters, and then reversing the process whenthe 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 thedirection that the current is flowing through the coil .

Read : that applying a magnetic field to a coil will cause an electricalcurrent to flow; this is used when reading back the previously writteninformation .

Newer (MR and GMR) heads don't use the induced current in thecoil to read back the information; they function instead by using the

principle of magnetoresistance , where certain materials change their resistance 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 changecorresponding to the stored patterns on the disk. A sensor is used to detect thesechanges 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 standardthin-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 theplatters than is possible with older designs, greatly increasing the storagecapacity 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 ferriteread/write head . The head is at the end of the slider, wrapped with the coil thatmagnetizes it for writing, or ismagnetized 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 issmaller and has a distinctive shape.

The actual head is too small to be seenwithout a microsco


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IDE/EIDE CONCEPTOverview 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 bus

standards: 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.


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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.

Contin ue


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IDE/EIDE CONCEPTATA-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 limitationthat stopped at 528MB.

Contin ue


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IDE/EIDE CONCEPT

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 in

capacity.

ATA-2 also known as fast-ATA or fast-ATA-2(Seagate/Quantum) and EIDE (Western Digital)


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IDE/EIDE CONCEPT

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.


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IDE/EIDE CONCEPTATA/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) whichallowed 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 acommon 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)


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IDE/EIDE CONCEPTATA/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.


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IDE/EIDE CONCEPT

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 as48-bit LBA or greater than 137GB support vendor.

CHS addressing made obsolete; drive must be use 28-bit or 48-bit LBA addressingonly.


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IDE/EIDE CONCEPT

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 ATA

standard. ATA-7 is last revision of the venerable parallel ATA standard. ATA is

evolving into Serial ATA which was incorporated into the ATA-7specification.


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IDE/EIDE Concept

SATA/ATA-8 began in 2004 which is a new ATA standard based on ATA-7 that carry forward the development of Serial ATA whileremoving parallel ATA from the standard entireky.Main features of SATA-8 include :

The removal of parallel ATA from the standardThe replacement of read long/write long functions.Improve HPA management.

SATA/ATAPI-8


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ATA Timeline

ATA-1 ATA-2

Drive support up to136.9GB;BIOS issuesnot addressed

Faster PIO modes;CHS/LBA BIOStranslation defined up to8.4GB;PC-Card

SMART; improvedsignal integrity; LBAsupport mandatory;eliminated single-wordDMA modes

PRESENT

ATA-5 ATA-6

ATA-7SATA

133MBpsUDMA mode;Serial ATA

Serial ATA II100MBps UDMA mode;extended drive andBIOS support up to144PB.

ATA-3 ATA-4

Ultra-DMAmodes; ATAPIPacketInterface; BIOSsupport up to136.9GB

Faster UDMAmodes; 80-pincableautodetectiopn

HARD DISK DRIVE TROUBLESHOOTING


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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 isusually 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 mechanicalhardware problems; instead, th ey are soft problem sthat can be solved by a new LLF and defect-mappingsession .

Soft problems are characterized by a drive that soundsnormal but produces various read and write errors .


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Hard Disk Drive Troubleshooting

And Repairing Hard problems are mechanical, such as when the drive

sounds as though it contains loose marbles . Constantscraping and grinding noises from the drive, with no reading

or 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-board

assembly . You can make this repair yourself and if successful, 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 .


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Hard Disk Drive Troubleshooting And Repairing

Testing 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.


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Hard Disk Drive Troubleshooting AndRepairing

Invalid 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 tableshave been damaged . No matter what, the drive must be partitionedand formatted before use . You also get this warning on FAT32 or NTFS partitioned drive if you use a Windows 95 (original version) or MS-DOS boot disk when checking .

Solution:

Use a Windows 95B, Windows 98/Me, or Windows 2000 boot diskto avoid this false massage from FAT32 partitions . Or, use a windows NT, Windows 2000 or Windows XP boot disk to

detect NTFS partitions.


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Hard Disk Drive Troubleshooting And

Repairing Invalid 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 driv es

existing partitions and either delete them and create new onesor keep the existing partitions and run FORMAT on each driveletter.


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Hard Disk Drive Troubleshooting

And RepairingDirectory of C:

Problem: The contents of the C: drive are listed, indicating the

drive was stored with a valid FDISK and FORMATstructure 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 availablesince October 1982 . In 2010, they remain the

standard physical storage medium for audio. Standard CDs have a diameter of 120 mm and can hold up

to 80 minutes of uncompressed audio (700 MB of data).


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The Mini CD has various diameters ranging from 60 to80 mm; they are sometimes used for CD singles or device 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, VideoCompact Discs (VCD), Super Video Compact Discs(SVCD), PhotoCD, PictureCD, CD-i, and Enhanced CD .


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Cross-section of a CD

A CD is a fairly simple piece of plastic, about four one-hundredths (4/100) of aninch (1.2 mm) thick . Most of a CD consists of an injection-molded piece ofclear polycarbonate plastic . During manufacturing, this plastic is impressedwith 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 thedisc, covering the bumps . Then a thin acrylic layer is sprayed over thealuminum to protect it. The label is then printed onto the acrylic. A cross sectionof a complete CD (not to scale) looks like this:


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How do CD-RWs rewriteable CDswork?

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

A flat reflective area represents a binary 1, while a non-reflective

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 read

The bumps on a CD are molded into the plastic when it is

perfect surface .bump represents a binary 0 .

digital data from the disc .

manufactured, so they are permanent .


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CD-R There are no bumps on a CD-R . A clear dye layer covers the CD's mirror. A write laser heats up the dye layer enough to

make it opaque . The read laser in a CD player senses the

difference between clear dye and opaque dyethe same way it senses bumps -- it picks up onthe difference in reflectivity .


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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 another temperature, 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 StandardThere 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 Memory and 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 or Write

CD-RW alias CD-E ReWritable or Erasable , The orange book standard references the fact that "Yellow" and "Red"

and data; although other colors (other CD standards) that do not mix are

introduced the standard for multisession writing

Once, Read Many

mix to orange; which means that CD-R and CD-RW is capable of music

capable of being burned onto the physical medium. Orange book also


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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 popular DVD 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 used

ISO 9660 defines a common logical format for files and directories so discs

operating systems (MS-DOS, Windows, Mac OS, UNIX, etc.) as well as

Due to the vast differences which exist among native file systems ISO 9660

restrictions upon the nature and attributes of files and directories .Three levels of interchange define these restrictions with level one being the

with some operating systems) .

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).

file format for data (CD-ROM) discs .

written to ISO 9660 specifications can be read by a wide array of computer

consumer electronics devices .

takes a lowest common denominator approach resulting in a variety of

most constraining and level three is the least (at the cost of compatibility

Various protocols are available to extend ISO 9660 to accommodate file


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CD Error Correction System

CD technology has built-in error correction systemswhich 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 of correction via the Layered Error Correction Codealgorithm .

With CIRC, an encoder adds two dimensional parityinformation, to correct errors, and also interleaves thedata 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 minor scratches.


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CD-ROM TroubleshootingMy CD-ROM/DVD drive doesn t work CD and DVD drives are some of the more failure-prone components in a PC. It is not uncommon for one to

suddenly 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 you re 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 allowedby 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.

e5164 Chapter-3-memory-Storage

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