Drives on magnetic disk

The Drives on flexible magnetic disk (NGMD) allow to carry the documents and program with one computer on another, keep information, not used on computer constantly, do the archive copies of the programme products, being kept on hard disk. The Most spreading has got the diskettes by size 5,25 and 3,5 inches that is to say 133 and 89 mms in diameter.

NGMD size 5,25 inches most often have a capacity by size 1,2 Mbytes and 360 Kbytes. Meet the diskettes of the former years of the issue, having smaller capacity or calculated on use in spindle with one head (the unilateral diskettes For writing and reading the diskettes by capacity 1,2 Mbytes are intended special drives, which are fixed on computer of the models IBM PC AT, and PS/2. Exist also special spindles on 360 Kbytes. The Technology record on data diskette different. In spindle by capacity 1,2 Mbytes are used heads for reading / record, providing more narrow track to information. For this purpose on 5,25 inch diskettes is used special magnetic covering, which allows to realize more thick zapisi. This magnetic covering harder to magnetize and degauss, than usual so such drives can be not used in spindle by capacity 360 Kbytes.
In computer of the last years of the issue more often started to use the drives for diskettes by size 3,5 inches (89 mms) and capacity 0,7 and 1,44 Mbytes. Transition on their use was is in the first place connected with tempestuous development portable computer, in which it is impossible was use the former drives because of greater sizes of the lasts.
NGMD size 3,5 inches are comprised, unlike 5,25 inch, in hard plastic envelope that vastly raises their reliability and longevity, as well as creates the significant comfort at transportation, keeping and use. In this connection the first from afore-mentioned disk displace last with computer market though they and cost(stand) several cherish.

Forming magnetic disk by size 3,5 inches and capacity 1,44 Mbytes (is hereinafter considered only he) are:

1. the lid defensive metallic;
2. the spring for lid metallic;
3. the envelope plastic (upper and lower sides);
4. two layings from soft paper;
5. the bolt of protection from record plastic;
6. the core of the disk metallic;
7. round reminding surface of the disk plastic, coverring magnetic

Record and sensing to information are realized by means of magnetic heads sailling type. They bear up on lever, which move on radius disk by means of special watching drive. 80 Tracks take seats On worker of the surfaces of the disk, 20 sectors. Density record is defined by value of the clearance between disk and magnetic head, but from stability of the clearance depends the quality a record (sensing).

Flesh memory

Follows to acknowledge that fact that digital technologies all broader fall into our life. For the last five years, appeared the ensemble different MR3-плееров, cameras, pocket computer and other digital equipment. But all this became possible due to creation compact and powerful processor. However when buying some device, fitting in pocket, does not cost(stand) be orientated on processor power only since in list priority she cost(stand)s far from on the first place.

At choice portable device the most important, on my glance - time of the autonomous work under reasonable mass and size of the element of the feeding. In многом this from memory, which defines the volume of the preserved material, and, length of the work without подзарядки battery. The Possibility of keeping to information in pocket device is limited modest power resource Memory, usually used in OZU computer, requires constant presenting the voltage. The Disc drives can save information and without unceasing presenting electricity, but then when writing and sensing data spend him(it) for three. Good output turned out to be флэш-memory, not running down spontaneous. The Carriers твердотельными are identified on her(its) base since have not moving parts. Regrettably, флэш-memory - an expensive pleasure: average cost of her(its) megabyte in eight once above aproximately, than beside SDRAM, not dialect uzh about hard disk. But here is absence of the movinging parts raises reliability флэш-memories: standard worker of the overloading are equal 15g, but short can reach 2000g, t. e. theoretically card must is exceed to work under greatly possible cosmic overloading, and bear the falls with трQхметровой of the height. Moreover in such condition is guaranteed operating the card before 100 years.

Many producers of the computing machinery see the memory future solely solid-state. The Effect this became practically simultaneous appearance on the market completing several standards флэш-memories.

Compact Flash

This standard was offered in 1994 company SanDisk, but in 1995 his(its) became to promote the assotiation CFA, created such large companies, as Hewlett-Packard, Hitachi, IBM, Motorola and others Presently in she enters already more than 165 companies.

The Modules to memories Compact Flash (CF) present itself modification PC-cards. The Truth, they less on volume and have whole 50 contacts instead of 68, but their possible connect in connectors PCMCIA through passive переходник without additional ON. The Device CF are divided on two types, outwardly differring thickness. The Sizes CF type I - 36,4x42,8x3,3 mm, but CF type II has same area, but their thickness more - 5 mm. Cards of the type II incompatible with connector of the type I then for cards of the type I approach the ports both type.

For functioning(working) the modules CF use the voltage 3,3 or 5 В and current before 100 mA. In total, on approving the producers, they comsume in 20 once energy less, than standard hard disks so not it is necessary often to change the batteries.

The Maximum capacity of the cards of the type I forms 256 Mbytes (beside companies PQI and Delkin), but cards of the type II - 512 Mbytes (beside company SiliconTech). Moreover the price exponential depends on amount of the module. The Memory of the type I cherish, than type II, since beside it ditto number of the microcircuits it is necessary to contain in smaller volume.

The Standard Compact Flash already enough is long ago submitted for the market so when buying the camera, working with card CF, possible have no doubt that will manage to find compatible on memories MP3-плеер and not to come to deal with card of the miscellaneous type. For joining of the card given type with ноутбуком it is enough to buy переходник for connector PCMCIA.

SmartMedia

The Standard SmartMedia, or SSFDC was designed in 1995 company Toshiba, but his(its) advancement concerns with the organization SSFDC Forum, in rows which much known companies. SSFDC (Solid State Floppy Disk Card) possible translate as "твердотельная diskette". Follows to note that many producers do флэш-cards immediately three main types: Compact Flash, SmartMedia and MultiMediaCard.

Unlike Compact Flash, the cards Smart Media (SM) are not provided with by built-in controller that, on замыслу creators, must reduce their cost. Besides, SM have a smaller sizes (37x45x1,76 mm) and mass (before 2). On popularity SM argue with CF, but together with him both these standards cover more halfs market флэш-cards.

The Worker of the voltage beside SM such, either as beside CF, but is usually used 3,3 V. Maximum capacity of the cards, declared producer, in particular companies EMTES and Delkin, forms 128 Mbytes. For want of internal controller for work with these card impossible to use passive переходник. SM are usually used in digital camera and MP3-плеерах, but here is in KPK - practically never.

MultiMediaCard

This standard has offered in 1997 companies Infineon Technologies (the subdivision Siemens) and SanDisk, but promotes his(its) assotiation MMSA, consisting of 80 companies (Infineon, Nokia, Ericsson, Hitachi, SanDisk, Motorola and others.).

The Cards MMS else less, than considered above, - 32x24x1,4 mm, yes and weigh they whole 1,5 So and are intended basically for ультрапортативных device, particularly actual they in KPK, cellular telephones and electronic notebook.

These modules to memories work at voltages 3,3 or 2,7 В and current before 35 mA, as conditions low энергопотребление.

Presently standard MMS already it is enough popular, and example that can serve his(its) support KPK Cassiopeia EM-500.

Secure Digital

The Company Matsushita Electronic (known under trademark Panasonic) together with SanDisk and Toshiba have developed the standard, in which have taken into account last winnowing of time. To prevent unauthorized copying, carriers Secure Digital (SD) is provided with means of protection from piracy.

The Sizes of the cards - 32x24x2,1 mm. Connectors for them compatible with module MMS. While standard only began to conquer the market, but producers promise already this year to raise the capacity of the cards SD before 256 Mbytes and above. Already issue is announced in format SD modem and other peripherals. But possibility of copyright protection has allowed the продавцам to release in selling the book and canto on these carrier.

Memory Stick

No time Sony has forced computer industry to choose as removable carriers their own 3,5-inch floppy-spindles, but now she has solved to take care of their own position and on аудиорынке, for what has developed the new standard флэш-cards Memory Stick.

(MS). These 10-contact device, size 21,5x50x2,8 mm and mass 4 become handhold to digital empire Sony, which installs them in their own digital плееры, фотоаппараты and video cameras, also toys and other device. At April 2001 was released, 128-Mbyte model MS. Also exists the variety MS Magic Gate (with protection from unauthorized copying), intended for плееров. At present standard Memory Stick is supported nearly solely device production concern Sony. Because of such not versatility they and have not got broad spreading.

Readers

For quick and suitable exchange by information between флэш-card and computer are used readers. They differ the way and interface of the connection to PC, as well as speed feature.

External readers

These device can be connected through USB, LPT, and FireWire(IEEE1394) interfaces. They differ the friend from friend only speed factor. The Velocity the most slow of them connected through parallel port, can reach 0,34Мбайт/with when writing, and 0,62Мбайт/with when reading data. Beside models 0,46 form with universal serial ports of these factors and 0,77Мбайт/with. But here is FireWire reader has left behind all their own rival far. The Device with data by interface capable to remember information on velocities before 0,7Мбайт/with, and give her(it) in three times quicker - 2,1Мбайт/with. Also big plus is an ability of some models to work nor with one, but with several standards флэш-memories.

Internal readers

Such a device are inserted in 3,5-inch compartment of the superblock, and are connected to ATA interface. To dignity of the readers given class pertain the high velocity(0,52 Mbyte/with and 1Мбайт/with) and absence stranger device on table. А to defect that he occupies the compartment of the superblock, and IDE channel.

Readers

This class device allows to connect флэш-card to computer through spindle. Is it Herewith used переходник outwardly look like 3,5-inch diskette (or PC-card for ноутбуков). The Card to memories is inserted in adapter, which subsequently takes seats in spindle. Use PCMCIA-adapter gives the not bad results, send rate reaches 1Мбайт/with. А when use floppy-spindle she недотягивает and before mark 36 Kbytes/with. And this besides that FDD(Flash Path)-adapter cost(stand)s cherish any other reader.

Technology CD & DVD

The Difference material registerring and reflecting layers. As registerring layer for disk CD-R the most wide-spread organic join the known under conditional names цианин (Cyanine) and фталоцианин (Phtalocyanine). Cianin has blue (cyan) colour (from which and occurs the name of the material, not having relations to cyanide - chemical derived циановодорода) and is characterized by average stability to irradiation by light swing temperature. Ftalocianin has a golden colour and vastly more rack to external influence. As reflecting material use the gold and silver, less aluminum and alloys. Accordingly, worker surface disk with reflecting слоем from colourless hurlled has a colour its registerring layer, but reflective layer from gild changes the colour цианина with blue on greenish. The Organic layer disk CD-RW usually has a sulphur-brown colour.

DVD - a videodisks, are befitted by CD. Under such motto will already begin the issue new device, signifying transition to 17-гигабайтным carrier data and digital video. The Time and us to get acquainted with novelty. About that that usual disks CD-ROM, given birth for writing the sound, not so uzh well suit for computer, the well-known since exist the difficulties вписывания free information in structure of the disk, corresponding to Red book. After several years of the discussion (and enough tough rivals) different variant perfected videodisks, September 15 1995 between different group developer was is finally reached principle consent about technical base of the making the new disk. the December 8 1995г. the most largest producers drive CD-ROM and in accordance with them device (Toshiba, Matsushita, Sony, Philips, Time Warner, Pioneer, JVC, Hitachi and Mitsubishi Electric) have signed the final agreement, having confirmed not only "nicety of" format, but also name of the novelty DVD (Digital Video Disk), HDCD (High Dencity CD - a disk to high density record), MMCD (MultiMedia CD). SD (Super Density - an сверхвысокой to density).

However, disputes around new standard were not terminated with taking the agreement - even name does not find autocratic support in rows of the founders more wide-spread is a version of the decryption of the abbreviation as Digital Versatile Disk (digital multifunctional) disk. If fate of the novelty will so successful, what foreshadow, that she can cause the revolution in computing machinery not only, but also in consumer electronics.

The Absence of the united understanding technical, and legal aspect of the new product obstructs not only preparation production, in spite of quickly expanding circle participant license agreements and begin issue first device.

Hardware

The First DVD forum also did not give the final editing a standard new carrier to information. DVD - how much, where and as. We shall Begin with technical features.

DVD can exist in several modifications. The most simple of them differ from usual disk only that that reflective layer is located not on forming nearly get fat thickness (1,2 mms) layer polycarbonate, but on layer of the half thickness (0,6 mms). The Second half - a flat upper layer. The Capacity of such disk reaches 4,7 GB and provides more than two hours video television quality (compression MPEG-2). Besides, without person of the labour on disk can be in addition saved high-quality стереозвук (on several languages!) and subtitles (also multilingual). If both layers carry information (in this case lower reflecting covering translucent), that total capacity forms 8,5 GB (certain reduction to capacities each layer is caused by need to shorten the sharing violations when sensing distant layer). Toshiba and Time Warner offer to use also two-way two-layer disk. In this case his(its) capacity will form 17 GB!

Already this features it is enough to visualize the influence, which can render such disk on cinema/видеоиндустрию. Not for nothing much dispute and delay with production device DVD is caused by co-ordination разнонаправленных ways of copyright protection. The Digital systems, as is well known, save the quality of the signal at copying and already does not serve the obstacle for making нелицензионных mines. So Assotiation кинопроизводителей America (MRAA - Motion Picture Association of America) with Assotiation of the producers of consumer electronics (Consumer Electronics Manufacturer's Association) discusses the possibility of встраивания protection from нелицензионного copyings right in device, as well as bills, connected with copyprotection. They Are Offered not only exception of the possibility of direct copying of the disk, but also more serious measures such as modification of the operating system for the reason недопущения copyings data, scanned with DVD on other nositeli. Radical measure - a modification of the architecture PC for the reason principle exception of the possibility of the hit DVD-given on system bus, whence they hereinafter can be copied.

The Working group (Technical Working Group), presenting interests of the producers computer, does not remain in side, since narrowing the functional possibilities device can turn out to be not painless. We shall Note only that if cinema/видеопроизводство will take DVD as carrier, that, considering very low cost of the copy of the disk under having a large circulation issue, possible expect really revolutionary changes to home electronics.

As is reached so significant increase the volume to information on DVD disk? For answer to this question we shall compare him(it) with familiar us CD-ROM. The Main difference, certainly, in raised density record to information. To account of the translation reading lazer from infrared range (the wavelength 780 nm) in red (with wavelength 650 nm or 635 nm) and increase the numeric equipment of the lens before 0,6 (against 0,45 in CD) is reached more then double compaction track and укорочение lengths reflecting drink (the salient/troughs).

Changed not only physical density of the accomodation to information on disk, but also ways of her(its) presentation. So, on change way to inflexions 8/14 (EFM - eight to fourteen modulation) came the way, named EFM+. He differs several other algorithms of the transformation and, the main, requires entering on border following friend for the other 14-bit codes not three, but only two additional bits, supporting condition to insufficiency of the sizes is drunk within the range of from 3 before 11 bits (t. e. between two consequent units after coding not less 2 and not more than 10 zeroes). Thereby, from each byte get not 14+3=17, but 14+2=16 code bit. Change the method to inflexions - only one of the ensemble форматных change, allowing as a whole enlarge the volume saved data. Strictly transition to EFM+ adds else nearly 6% to volume of the disk. The more powerful mechanism to correction error RS-PC (Red Solomon Product Code) promises to be on order more firm to possible error of the reproduction.

From unnamed else features shall note the nominal send rate given - 1108 Kb/with, supported under constant linear velocity (CLV - constant lineal velocity) 4 m/with.

Does Not follow be specifically tempted - increases on order as well as volume data, which we wanted read without error. Besides, sharp reduction separate element on reflecting surfaces will inevitably bring about increase amount casual malfunctions when reading.

Author: А. V. Savin It Is Added: 03.05.2007