Test. External (long-term) memory The principle of changing the magnetic induction of the media surface
MINISTRY OF EDUCATION OF THE RUSSIAN FEDERATION
Stavropol Technological Institute of Service
YURGUES branch
Test
subject___________________________________________________________________
_______________________________________________________________________
by discipline Computer science
Performed by a student of group IST 031 ZU _______________ « »
Checked by Ph.D., Associate Professor _______________ ""
Stavropol 2003
Introduction........................................................ ...............................................
1. Types of magnetic disk drives....................................................
2. Floppy disk drives....................................................
3. Hard disk drives....................................................
Conclusion................................................. ...........................................
Sources of information used.........................................................
Introduction.
Manufactured information storage devices represent a range of storage devices with different operating principles, physical and technical performance characteristics. The main property and purpose of information storage devices is its storage and reproduction. Storage devices are usually divided into types and categories in connection with their operating principles, operational, technical, physical, software and other characteristics. For example, according to the operating principles, the following types of devices are distinguished: electronic, magnetic, optical and mixed - magneto-optical. Each type of device is organized based on the corresponding playback/recording storage technology digital information. Therefore, due to the type and technical performance Information carriers are distinguished: electronic, disk and tape devices. Let us pay special attention to magnetic disk drives – hard magnetic drives.
1. Types of magnetic disk drives
Magnetic disks are used as storage devices that allow you to store information for a long time, even when the power is turned off. To work with Magnetic Disks, a device called a magnetic disk drive (MDD) is used.
Main types of storage devices:
· floppy magnetic disk drives (FMD);
· hard magnetic disk drives (HDD);
· magnetic tape drives (NML);
· CD-ROM, CD-RW, DVD drives.
The main types of media correspond to them:
flexible magnetic disks ( Floppy Disk ) (diameter 3.5'' and capacity 1.44 MB; diameter 5.25'' and capacity 1.2 MB (currently outdated and practically not used, production of drives designed for disks with a diameter of 5.25'', also discontinued)), disks for removable media;
· hard magnetic disks ( Hard Disk );
· cassettes for streamers and other NML;
· CD-ROM, CD-R, CD-RW, DVD discs.
Storage devices are usually divided into types and categories in connection with their operating principles, operational, technical, physical, software and other characteristics. For example, according to the operating principles, the following types of devices are distinguished: electronic, magnetic, optical and mixed - magneto-optical. Each type of device is organized on the basis of the corresponding technology for storing/reproducing/recording digital information. Therefore, in connection with the type and technical design of the information carrier, they distinguish: electronic, disk and tape devices.
Main characteristics of drives and media:
· speed of information exchange;
· reliability of information storage;
· price.
Let's take a closer look at the above drives and media.
Principle of operation magnetic storage devices based on methods of storing information using the magnetic properties of materials. Typically, magnetic storage devices consist of information reading/writing devices And magnetic media, to which recording is directly carried out and from which information is read. Magnetic storage devices are usually divided into types in connection with their design, physical and technical characteristics of the storage medium, etc. The most common distinctions are made between disk and tape devices. The general technology of magnetic storage devices consists of magnetizing areas of the media with an alternating magnetic field and reading information encoded as areas of alternating magnetization. Disk media, as a rule, are magnetized along concentric fields - tracks located along the entire plane of the discoidal rotating media. Registration is made in digital code. Magnetization is achieved by creating an alternating magnetic field using read/write heads. The heads are two or more magnetic controlled circuits with cores, the windings of which are supplied with alternating voltage. A change in voltage causes a change in the direction of the magnetic induction lines of the magnetic field and, when the carrier is magnetized, means a change in the value of the information bit from 1 to 0 or from 0 to 1.
Usually the NMD consists of the following parts:
- disk drive controller,
- the disk drive itself,
- interface cables,
- magnetic disk
A magnetic disk is a magnetically coated base that rotates around an axis inside the drive.
The magnetic coating is used as a storage device.
Magnetic Disks are: hard (Winchester) and flexible (Floppy).
Hard disk drive - HDD.
Floppy disk drive - NGMD(FDD).
In addition to HDD and HDD, they are often used removable media. A fairly popular storage device is Zip. It is available as integrated or stand-alone units connected to a parallel port. These drives can store 100 and 250 MB of data on cartridges resembling a 3.5” floppy disk, provide an access time of 29 ms and data transfer speeds of up to 1 MB/s. If a device is connected to the system via a parallel port, then the data transfer rate is limited by the speed of the parallel port.
The Jaz drive is a type of removable hard disk drive. The capacity of the cartridge used is 1 or 2 GB. The disadvantage is the high cost of the cartridge. The main application is data backup.
In magnetic tape drives (most often such devices are streamers) recording is made on mini-cassettes. The capacity of such cassettes is from 40 MB to 13 GB, the data transfer speed is from 2 to 9 MB per minute, the tape length is from 63.5 to 230 m, the number of tracks is from 20 to 144.
2. Floppy disk drives.
Floppy drives(floppy disks, floppy disks) allow you to transfer documents from one computer to another and store information. The main disadvantage of the drive is its small capacity (only 1.44 MB) and unreliable information storage. However, this method is the only way for many Russian users to transfer information to another computer. Computers of recent years are equipped with 3.5-inch (89mm) floppy disk drives. Previously, 5.25-inch drives were used. Despite their size, they have a smaller capacity and are less reliable and durable. Both types of floppy disks are write-protected (a jumper on the floppy disk's protective casing). IN Lately began to appear alternative devices: external drives, with disk capacities up to 1.5 GB and much more higher speed reading devices rather than a floppy disk drive, but they are still not widespread and are very expensive.
Storage on a removable flexible magnetic disk (floppy). The floppy disk has a plastic base and is housed in a special plastic casing. The floppy disk is inserted into the FDD along with the casing. The floppy disk (in FDD) rotates inside the casing at a speed of 300 rpm. On this moment IBM PC uses 2 types of FDD: 5.25" and 3.5". The 5.25" floppy disk is enclosed in a flexible plastic casing. The 3.5" floppy disk is enclosed in a rigid plastic casing. HDDs are faster devices than FDDs.
A floppy disk or floppy disk is a compact, low-speed, low-capacity means of storing and transferring information. There are two sizes of floppy disks: 3.5”, 5.25”, 8” (the last two types are almost out of use).
3.5" floppy disk 5.25" floppy disk
Structurally, a floppy disk is a flexible disk with a magnetic coating, enclosed in a case. The floppy disk has a hole for the drive pin, a hole in the case for accessing the read-write heads (3.5” covered with an iron shutter), a cutout or write protection hole. In addition, a 5.25" floppy disk has an index hole, and a 3.5" high-density floppy disk has an index hole (high/low). A 5.25" floppy disk is write-protected if the corresponding cutout is closed. A 3.5” floppy disk is the opposite - if the protection hole is open. Currently, 3.5" high-density floppy disks are almost exclusively used.
The following notations are used for floppy disks:
SS single side - one-sided disk (one working surface).
DS double side - double-sided disc.
SD single density - single density.
DD double density - double density.
HD high density - high density.
A floppy drive is fundamentally similar to a disk drive. hard drives. The rotation speed of a floppy disk is about 10 times slower, and the heads touch the surface of the disk. Basically, the structure of information on a floppy disk, both physical and logical, is the same as on a hard disk. In terms of logical structure, the floppy disk does not have a disk partition table.
Operation of the float drive controller It is convenient to consider separately in the modes of writing and reading a byte of data.
The recording mode is activated by the low level of the PC0 line (pin 14 DD1). In this case, the float drive is switched to the “Record” mode (the WRDATA signal is active). The byte being written is entered into port A and its eight-bit code is sent to the input of the multifunctional register DD2. The operating mode of this register is controlled by the bit counter DD9 and the decoder DD10. After writing the previous byte, the counter is in a reset state, and logical zero signals are present at all its outputs. In this state of the input signals, the DD10 decoder at pin 7 generates a logical zero signal, which, together with the low level at pin 2 of the DD17.1 element, allows writing parallel code to the DD2 register. In any other state of the counter, the register is put into shift mode.
Low level PC0 on element DD13. 4, the channel for reading information from the float drive RDDATA is blocked. A logical zero arriving at the S inputs of the DD11.1 trigger after the blocking signal is inverted by the DD14.1 element sets a logical one at pin 5 of the DD11.1 trigger. Through the inverter DD14.3, a low level signal is supplied to the reset inputs of the counters DD7 and DD8, which ensures their continuous operation. The signals taken from the 8th and 9th pins of the DD8 counter, on the elements DD14.4, DD15.1, DD15.2, form the ISS and ISD sequences, respectively. The ISD pulse, after inverting by element DD14.6, is supplied to the clock input of register DD2. When a clock pulse arrives, the parallel code written in the register is shifted to the right, and the next bit of this code appears at pin 20. Recording signals are generated by elements DD13.1, DD13.2 and DD13.3. At the moment of action high level The ISD at pin 2 of DD13.1 has a writable bit. Through elements DD13.1 and DD13.2, the bit is supplied to the input of the buffer amplifier DD6, and then to the HDD recording signal line (WRDATA). According to the timing diagram shown in Fig. 8, the ISS signal is at this time in a state of logical zero. Therefore, the passage of signals through element DD133 is prohibited. After the ISD signal goes into a logical zero state, the passage of the information bit for writing through the DD13.1 element will become impossible. When the ISS level is active, through open elements DD13.3, DD13.2 and buffer DD6, a logical unit generated at pin 12 of the decoder DD10 will be sent to the WR DATA line. Thus, at the moment the ISD is operating, information bits will arrive on the NGMD recording line, and at the moment the ISD is operating, single synchrobits will arrive. The number of recorded bits is counted by counter DD9. After the eighth pulse of the ISD has passed, its outputs will go to the zero state, which will cause the installation of a readiness trigger: a logical one will appear at pin 9 of DD12.2. The state of the readiness trigger is programmatically polled by the DOS via the PB7 line. When a one is detected in this bit, the PC will write a new byte to port A of DD1 (address F000H), and a readiness trigger reset signal will be generated on elements DD15.4, DD16.4, DD16.1, DD16.2. Thus, information is written and read on the float drive.
3. Hard disk drives (HDD)
Hard disk drives (hard drives) are intended for permanent storage of information used when working with a computer: operating system programs, frequently used software packages, document editors, translators from programming languages, etc. Having a hard drive greatly improves the usability of using a computer. For the user, hard disk drives differ from each other primarily in their capacity, i.e. how much information fits on the disk. Nowadays, computers are mostly equipped with hard drives of 520 MB or more. Computers operating as file servers can be equipped with a 4-8 MB hard drive or more than one.
A storage device on a non-removable magnetic disk, created on the basis of special. technology (Winchester technology - hence the name). The Winchester magnetic disk (on a metal base) has a high recording density and a large number of tracks. A Winchester can have several Magnetic Disks. HDDs of the Winchester type were created in 1973. All Winchester magnetic disks (combined into a package of disks) are hermetically packaged in a common casing. Magnetic disks cannot be removed from the HDD and replaced with similar ones!!!
The magnetic heads are combined into a single unit (magnetic head unit). This block moves radially in relation to the disks. While the PC is running, the Disk Pack rotates all the time with constant speed(3600 rpm). When reading/writing information, the block of magnetic heads moves (positions) to a given area, where sector-by-sector reading/writing of information is performed. Due to the inertia of the information processing process and the high speed of rotation of the disk package, a situation is possible when the magnetic head unit does not have time to read the next sector. To solve this problem, the sector alternation method is used (sectors are numbered not in order, but with gaps). For example, instead of numbering the sectors in order: 1 2 3 4 5 6 7 ..., they are numbered like this: 1 7 13 2 8 14 3 9 ...
Recently, faster SCSI controllers have appeared that provide sufficient information processing speed, and the need for sector interleaving is eliminated.
So, the drive contains one or more disks (Platters), i.e. This is a carrier that is mounted on an axis - a spindle, driven by a special motor (part of the drive). The engine speed for conventional models is approximately 3600 rpm. It is clear that the higher the rotation speed, the faster information is read from the disk (of course, at a constant recording density), however, the media platters can simply be physically destroyed at high speeds. However, in modern models hard drives rotation speed reaches 4500, 5400 or even 7200 rpm.
The disks themselves are ceramic or aluminum plates processed with high precision, onto which a special magnetic layer (coating) is applied. In some cases, even glass plates are used. It should be noted that in recent years the technology for manufacturing these parts has come a long way. In older drives, the magnetic coating was usually made of iron oxide. Currently, gamma ferrite oxide, isotropic oxide and barium ferrite are used for coatings, but the most widely used are disks with a deposited magnetic layer, or more precisely, with a metal film (for example, cobalt).
The number of disks can be different - from 1 to 5 and higher, the number of working surfaces is correspondingly 2 times greater, although not always. Sometimes the outer surfaces of the outer disks or one of them are not used for data storage, and the number of working surfaces is reduced and may be odd.
The most important part of any drive is the read/write head. As a rule, they are located on a special positioner, which resembles the pickup lever on a record player (tonearm). This is the rotating head actuator. By the way, there are also linear positioners, whose principle of movement is reminiscent of tangential tonearms.
Currently, there are at least several types of heads used in hard drives: monolithic, composite, thin-film and magnetic-resistance (MR). Monolithic heads are usually made of ferrite, which is a fairly brittle material. In addition, the design of such heads fundamentally does not allow high recording densities. Composite heads are smaller and lighter than monolithic heads. This is usually glass on a ceramic base; for example, alloys are used that include materials such as iron, aluminum and silicon. Ceramic heads are more durable and provide a closer distance to the magnetic surface of the media, which in turn leads to increased recording density. In the manufacture of thin-film heads, a photolithography method is used, which is well known in the semiconductor industry. In this case, a layer of conductive material is deposited on a non-metallic substrate.
Magnetic-resistive heads developed by IBM are currently considered one of the most promising. Fujitsu and Seagate also began their production. The magnetic-resistive head itself is an assembly of two heads: a thin-film one for writing and a magnetic-resistive one for reading. Each head is optimized for its own task. It turns out that a magnetic-resistive head is at least three times more efficient than a thin-film head when reading. If the thin-film head has a conventional inductive operating principle, i.e. alternating current generates a magnetic field, then in a magnetic-resistive (by definition) change in the magnetic flux changes the resistance of the sensitive element. Magnetic-resistive heads, compared to others, make it possible to increase the recording density on the media by almost 50%. All modern hard drives from IBM are equipped only with these heads. New IBM developments in the field hard drives allow for a recording density of 10 Gbit per square inch, which is about 30 times more than now. We are talking about Giant MR heads.
Note that in modern hard drives the heads seem to “fly” at a distance of a fraction of a micron (usually about 0.13 microns) from the surface of the disks, without touching them. By the way, in hard drives produced in 1980 this distance was another 1.4 microns, but in promising models it is expected to decrease to 0.05 microns.
On the first models of hard drives, the head positioner was usually moved using a stepper motor. Currently, linear (voice coil, or “voice coil”) motors, otherwise called solenoid motors, are predominantly used for this purpose. Their advantages include a relatively high speed of movement, practical insensitivity to changes in temperature and position of the drive. In addition, when using solenoid motors, automatic parking of the write/read heads is realized when the power to the hard drive is turned off. Unlike drives with a stepper motor, periodic reformatting of the media surface is not required.
The head movement drive is a closed servo system, the normal functioning of which requires pre-recorded servo information. It is this that allows the positioner to constantly know its exact location. The positioning system may use dedicated and/or working surfaces of the media to record servo information. Depending on this, dedicated, integrated and hybrid servo systems are distinguished. Dedicated systems are quite expensive, but have high performance, since they spend virtually no time receiving servo information. Built-in servo systems are significantly cheaper and less critical to mechanical shocks and temperature fluctuations. In addition, they allow you to save more on disk useful information. However, such systems tend to be slower than dedicated systems. Hybrid servo systems take advantage of the above two, i.e. large capacity and high speed. Most modern hard drives for mass use use built-in servo information.
In addition to all of the above, inside any hard drive there must be printed circuit board With electronic components, which are necessary for the normal functioning of the drive device. For example, the electronics deciphers the commands of the hard disk controller, stabilizes the engine rotation speed, generates signals for the write heads and amplifies them from the read heads, etc. Currently, a number of hard drives even use DSP (Digital Signal Processor) digital signal processors.
An essential component of most hard drives are special internal filters. For obvious reasons, it is of great importance for work hard disks has the frequency of the surrounding air, since dirt or dust can cause the head to collide with the disk, which will definitely lead to its failure.
As you know, to install disk drives in system unit Any personal computer has special mounting compartments. The overall dimensions of modern hard drives are characterized by form factor. The form factor indicates the horizontal and vertical dimensions of the hard drive. Currently, the horizontal size of a hard drive can be determined by one of the following values: 1.8; 2.5; 3.5 or 5.25 inches (the actual size of the hard drive case is slightly larger). The vertical size is usually characterized by such parameters as Full Height (FH), Half-Height (HH), Third-Height (or Low-Profile, LP). “Full” height hard drives have a vertical dimension of more than 3.25’’ (82.5 mm), “half” – 1.63’’ and “low profile” – about 1’’. It must be remembered that to install a drive that has a smaller form factor than the mounting bay in the system unit, you will have to use special fasteners.
Conclusion
The development of the electronics industry is carried out at such a rapid pace that literally in one year, today's “miracle of technology” becomes obsolete. However, the principles of a computer remain unchanged.
According to experts, soon the company will no longer equip personal computers with disk drives - they will be replaced by USB flash drives with a capacity of 16 megabytes, which are initially supposed to be installed on computers hi-end class, and then, with a positive reaction from customers, to all desktops. Dell has already removed disk drives from standard laptops. Macintosh computers have not had floppy drives for five years.
CDs and DVDs may be at the forefront of data storage technology, but the rather old-fashioned mechanical tape drives still play an important role in storing large amounts of information. Moreover, this role is so great that IBM scientists have developed a mechanism for recording 1 terabyte (which is 1 trillion bytes of data) on a linear digital tape cartridge. This value, according to the developers, is approximately 10 times greater than any other tape drive capacity currently available. This amount of information is equivalent to 16 days of continuous DVD video playback, or 8,000 times the amount of information that the human brain retains over a lifetime. Although a magnetic tape drive is difficult to imagine in a home interior on desktop PCs, for medium and large businesses this technology remains quite relevant for backup data storage, and the tape is less vulnerable to hacking and theft of information. Latest technology allows you to pack a drive with a high data recording density so that it becomes quite compact. In the long term, it is possible to reduce companies' costs for data storage. While the current average cost of storing information on magnetic tape is about $1 per GB, it is possible to reduce these costs to 5 cents per GB. For comparison, the cost of storing 1 GB of information on a hard drive is now $8-10, and on semiconductor-based devices it is about $100 per GB. New ML data storage technologies will play an important role in information-intensive industries such as mining or archives. Also, the need to increase the volume of stored information arises among corporations and scientists in all disciplines, from geophysics to sociology. For example, academic pursuits require a system that allows long-term re-access to data with the ability to create multiple copies and easily move them anywhere. The first magnetic tape drive was created 50 years ago, when the IBM Model 726 could store only 1.4 MB of information, approximately as much as can now fit on a regular floppy disk, and the tape reel was about 12 inches in diameter. For comparison, latest development IBM specialists with 1TB of storage capacity fits into a cartridge the size of a postal envelope, and the volume of information stored in it is equivalent to the contents of 1,500 CDs. According to company representatives, the plan for possible mass production of terabyte cartridges will include the release of intermediate products over several years. During this time, it is planned to release cartridges with a capacity of 200,400, and then 600GB.
Researchers managed to make a magnetic film from an alloy of cobalt, chromium and platinum. They then used a focused ion beam to cut the film into rectangular magnetic “islands” measuring just 26 millionths of a millimeter across. This corresponds to a recording density of 206 GB per square inch. True, in this case it will not be possible to write and read information directly, since the size of the heads is much larger than the size of the “islands”. Therefore, new, smaller heads are needed. In addition, the write and read procedures will need to be effectively synchronized with the movement of the heads. The prototype developed at IBM implements such synchronization, but widespread adoption of such systems will require significant improvements in hard drive technology.
Sources of information used
1. Leontyev V.P. PC: universal user guide Moscow 2000.
2. Figurnov V.E. IBM PC for the user. 5th edition St. Peretburg, JSC “Koruna” 1994.
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Device for emergency destruction of information from magnetic media 2S-994 “Priboy”
Apparently, even a child already understands that in our new information age, huge capital is invested not so much in “the main means of production” (that is, in equipment, fuel, Consumables and other completely material substances), as well as immaterial concepts of data, information, intellectual property and other “nonsense”. Which, due to its immateriality, is often still judged very frivolously - especially due to the widespread prevalence of piracy and the “openness” and publicity of many information resources. At the same time, the volume and role of “just information” in the modern world is growing at an alarming rate, and its importance and cost for interested parties is sometimes incomparably higher than the cost of completely material substances. And the development of computer technology has played a huge role in this, by now almost completely displacing non-electronic sources of storage, processing and transmission of information from the market. These development trends in the modern world, on the one hand, require steadily improving the quality and reliability of electronic data storage systems. On the other hand, make sure that in case of an emergency your precious data does not fall into unwanted hands. And today we have a device in our field of vision that contributes precisely to the latter situation - that is, a destroyer of information from magnetic storage media, suitable for both corporate and “personal” use, including as part of a regular PC.
Let us immediately point out that the device for emergency destruction of information from magnetic media “Priboi” (2C-994) considered here, produced by the domestic company “” and recommended as a means of protecting individual workplaces for working with information that does not constitute a state secret, is not sold in regular stores. computer stores. But you can still find him there - as part of the “most ordinary” personal computers(system units) IRBIS company "", which provided it to us for testing.
Such a computer, accordingly, has increased security and is optimal for government agencies, financial institutions and simply “ good people" :) The device for emergency destruction of information from a hard drive is designed, as you may have guessed, for the emergency destruction of information and disabling the installed computer hard disk at the user's initiative when attempting unauthorized access. After this, the manufacturer guarantees that no computer will be able to recognize your disk, and no one will be able to read/recover the information stored on it. The device does not have any effect on the operation of the computer - both in standby mode and in destroy mode. And the impulse destroys information and disables only this hard drive, without having any effect on other components of the computer. The device can be used regardless of the computer operating mode, even if the PC is disconnected from the network.
Appearance and structure of "Priboy"
One can only rejoice at the sense of humor of the creators of “Surf”, who gave such a playful name to a device capable of “nailing” a hard drive in the bud - overseas colleagues would probably have come up with something worse like a “terminator-eliminator” or, even worse, would have named it after it your wife/girlfriend/dog. :)
Since this device is part of the K-Systems computers, there is obviously no point in talking about branded packaging and retail delivery kit. Therefore, let's say that the shredder itself is transported in a small cardboard box with an identifying sticker. 
The Priboy package includes the shredder unit itself, several mounting screws (for fixing the hard drive in the unit and the unit itself in the PC case), short description, set of radio receiver and remote control controls (radio transmitter, 2 pcs.), bar on back panel PC case with the necessary controls, indications and an AC power cord. 
The Surf destroyer is a heavy metal rectangular block designed for installation in a five-inch bay of a PC system unit, inside which electronics and a controlled electromagnet are located. 
On the top of the case there is a seat for attaching a destroyable (“beatable”) hard drive of the 3.5-inch form factor, and the hard drive is supposed to be installed “upside down”, that is, with the board facing out and the top cover down - almost close to the cutout in metal case“Surf”, which (cutout) is covered with plastic (see photo above). 
In this form, the shredder with an installed hard drive occupies two standard five-inch compartments of the computer system unit in height (in the photo - the two lower compartments), 
and thanks to the appropriate arrangement of the side mounting holes, it can be hidden from the front by the usual front false panels of the compartments of this case (as if there was nothing there;)). 
The “front” part of the shredder body has only holes for ventilation, but rear end equipped with two “proprietary” connectors, 
one of which serves to supply power (directly from the 220 volt AC network; “Priboy” does not use any power from the computer!), and the other is connected to control and indication signals. Both cables (power and signals) are supplied to the unit from a strip mounted on the rear panel of the PC case. 
Through it, a power cord is inserted into the case, and on the bar itself there is an LED to indicate the current state of the device and a button, by pressing which you can “kill” the hard drive, that is, destroy all data on it. However, going “to the rear” of the case for this may not be very convenient (especially if you need to act quickly, and the system unit is under a table or in a cabinet; by the way, you need to be careful about accidentally pressing this button during other actions, for example, connecting cables at the back). Therefore, to facilitate the destruction of data, a radio unit is included with the “Priboy” remote control, which (according to the manufacturer) is capable of signaling destruction from a distance of up to 100 meters. 
The radio unit consists of a small transmitter connected inside the PC case to the contacts of the signal connector of the exterminator and equipped with a 15-centimeter piece of wire as an antenna, and a remote control transmitter with four buttons that must be pressed sequentially to obtain the desired effect.
The receiver is also equipped with a service LED that blinks in time with the button presses on the transmitter (if the latter has a working battery, which is better to take care of in advance, since it uses a not very widely used 12-volt battery in A23 format - 28 mm long and 10 mm in diameter). The transmitter board itself uses a common microcircuit, one transistor and less than a dozen passive radio elements. 
The body of the destroyer, unfortunately, is fastened with rivets, so we were not able to disassemble it non-destructively in order to study the insides. Obviously, there is a network power supply, simple control electronics and a controlled electromagnet, which produces a powerful demagnetizing pulse to the hard drive.
Operating principle
The operating principle of Priboy is quite obvious: if data on a hard drive is stored in the form of magnetized sections of a ferromagnetic surface, then these sections need to be remagnetized or demagnetized (orient the magnetic domains randomly). It is necessary to locally influence the disk with a powerful magnetic pulse. Demagnetization devices have long been widely known in technology, and the only thing left is to adapt one of these devices for computer hard drives and select required modes demagnetization/remagnetization.
It was this path that the manufacturer of “Priboy”, the company “” (KSU), took. The main and only activity of this company is development and production various devices emergency destruction of information from magnetic media (hard drives, floppy disks, streamer cartridges, audio and video cassettes):
- while working with information (protection of any types of servers, including Rackmount 19″) using Priboy and 2S-994V devices in manual mode, and the Tsunami complex in automatic.
- during transportation - the “Shadow” case.
- during storage - information safe "Mig".
- when disposing of media containing confidential information- recycler "2S-994U".
KSU has a license from the FSB of Russia for the right to use information constituting state secrets, licenses from the State Technical Commission of Russia, the Ministry of Defense of the Russian Federation for activities in the field of development and production of information security means. 
The production of data destruction devices is certified according to the ISO-9001 quality system. 
(By the way, the computer manufacturer K-Systems also has various licenses and certificates for the production of equipment for defense departments.)
Copyright to the equipment produced is confirmed by patents from Russia and Ukraine. Basic destruction units are certified by the State Technical Commission of Russia, the Ministry of Defense, the Military Register and the State Standard of Russia for compliance with the only document currently regulating the destruction of information from magnetic media - the Order of the Ministry of Defense Russian Federation No. 306 of August 10, 2002 
Among KSU's clients are Sberbank and the Central Bank of Russia, the Ministries of Defense and Internal Affairs, and the largest commercial structures.
For a better understanding of the processes taking place, let us quote excerpts from the manufacturer’s description of the operating principle of the shredder.
“A distinctive feature of ferromagnets is the presence of macroscopic volumes of matter - domains in which the magnetic moments of atoms (ions) are oriented in the same way. Domains have spontaneous magnetization (magnetic moments) even in the absence of an external magnetizing field. In a ferromagnet that has not been exposed to external magnetic fields, the magnetic moments of the different domains are usually mutually compensated, and their resulting magnetic field is close to zero. Ferromagnetic materials are characterized by hysteresis when magnetization is reversal by an external magnetic field, that is, a delay in changes in the magnetization of a substance from changes in the magnetizing field. The figure shows the main characteristic of ferromagnets - the dependence of magnetic induction IN from tension N magnetizing field (the so-called hysteresis loop).
Hysteresis loop of a ferromagnet.
“Under the influence of an external magnetic field, the orientation of elementary magnetic fields created by the circular motion of electrons in the atoms and molecules of a ferromagnet occurs. As a result, the sizes of magnetic domains oriented in the direction of the external field increase. After the cessation of external influence, the changes that occurred in the size and orientation of the magnetic domains are partially preserved. Residual magnetization of the substance appears - a trace left in the ferromagnet by external influences. It is this residual magnetization of the carrier material that is then recorded by devices that read the recorded information.
“The dependence of the magnetization of a ferromagnet on changes in the external magnetic field is nonlinear. Magnitude IN s characterizes the state of saturation of the material, in which an increase in the external magnetic field no longer leads to changes in its domain structure or to a further increase in its magnetization. In this state, the magnetic fields of all domains are oriented identically under the influence of an external magnetic field, and their total magnetic field reaches the maximum possible value. Magnitude Br characterizes the limiting residual magnetic field (magnetization) of the material after the cessation of exposure to an external field sufficient to saturate the ferromagnet.
“The use of the dependence of the residual magnetization of ferromagnetic materials on the magnitude of the external magnetizing field underlies the process of recording information on magnetic media. Information is recorded by sequentially applying an external magnetic field, varying according to the law of the informative signal, to various sections of the medium, made in the form of wire, tape or disk, and reading it by sequentially recording the residual magnetization of these sections.
“Understanding the physics of these processes makes it easy to imagine a standard procedure for “erasing” recorded information for various devices. Typically, erasing is carried out by exposing the carrier to an external magnetic field through the relative movement of the magnetic carrier and a special erasing magnetic head to which the D.C. or high frequency current. In the first case, erasing is carried out by reversing the magnetization of all sections of the information carrier with a constant magnetic field, and in the second, by reversing them with an alternating magnetic field. This method of destroying information is quite simple, but it requires significant time, comparable to the duration of the record being destroyed. As for the reliability of information destruction, it is low. This is due to the fact that usually standard erasing devices of recording equipment do not provide the level of external magnetic field required for magnetic saturation of the carrier material. As a rule, microregions (small-volume magnetic domains) oriented in the direction of the previous external magnetic influence remain on areas of the working surface of the carrier. The residual magnetization of these areas is relatively small and may not be registered by a standard device. However, with a detailed analysis of the fine structure of the magnetic field created by the area of the working surface of the carrier under study, traces of previous external magnetic influences are detected quite easily. These traces allow, if necessary, to restore information destroyed by the erasure procedure.
“Slightly higher reliability of information destruction is ensured by recording new information over the destroyed one. However, even in this case, the original information can be restored using special methods. Currently, specialists have at their disposal several methods for restoring destroyed information, differing in physical approaches to recording the fine structure of the magnetization fields of the information carrier. These methods, applicable both to the whole medium and to its individual fragments, make it possible to analyze records destroyed as a result of repeated rewriting (up to five layers) of new information onto this medium.
“In many cases, acceptable reliability of destruction of computer information is ensured by reformatting the magnetic storage medium: floppy disk or computer hard drive. However, this operation is quite time-consuming, not always convenient, and also does not guarantee the irrecoverability of information. The same methods for studying the fine structure of magnetization fields allow specialists, if necessary, to restore a recording destroyed by reformatting. Thus, standard operations of erasing and rewriting information in conventional audio and video recording equipment, as well as known software methods destruction of computer information requires a lot of time and can provide acceptable reliability of information destruction only from such a potential “information restorer”, who only has at his disposal standard means information processing: PC, audio or video recorder, etc.
“At the same time, special requirements are imposed on the quality of destruction of information of a high level of secrecy (for example, information constituting a state secret). For such information, philistine ideas about its “reliable” erasure are no longer enough. Well-defined guarantees of its destruction are needed. The “guaranteed” destruction of protected information usually means the impossibility of its recovery by qualified specialists (experts) using any known restoration methods. To destroy such information, you have to resort to specially designed devices or other, more radical methods of destroying it than those already discussed.
“Most of the currently known industrial developments in the field of destruction of information on magnetic media are based on bringing the material of the information carrier to a state of magnetic saturation. As an example, we can point to a device manufactured in JapanSR1, designed for quickly erasing audio recordings from standard voice recorder microcassettes. By its design, it is a powerful permanent magnet, between the poles of which it is necessary to manually stretch an erasable microcassette. It should be noted that we were unable to find studies confirming the guaranteed destruction of information recorded on a microcassette by this device. However, it is quite obvious that in order for similar devices to quickly destroy information recorded on large-sized media (for example, on a video cassette standardVHS), permanent magnets of much larger weights and dimensions will be required. In many cases, the use of such magnets may not be acceptable even for environmental reasons.
“The use of information destruction should be considered much more promising.a briefly created powerful electromagnetic field sufficient to magnetically saturate the carrier material. This method of erasing records by magnetizing the media with a pulsed magnetic field of a certain magnitude and orientation has been patented by domestic specialists. Using this method, various products designed for quick (emergency) erasing of information recorded on magnetic media of various types have been developed and launched.”
And it is this method that is used in the device described here. The seriousness of the approach of the creators of “Priboy” is evidenced by the fact that in 2003 its developers received a Russian utility model patent number 32628: 
The description of the patent, in particular, states that the device for erasing a record from a magnetic storage medium consists of a control unit for the erasure process, at least two magnetic field formation circuits and two sensors of the amplitude-time parameters of the magnetic field. Each circuit contains a power source, a switch, a capacitor, and an inductor, and the inductors of the two indicated circuits form a solenoid, inside which a magnetic storage medium is located. The coils are installed so that the magnetic field vectors of these circuits are parallel to each other and perpendicular to the magnetic field vector generated when recording on a magnetic medium. 
Additionally, the device can use coils of different shapes and mutual placement, storage cooling with a temperature sensor and a diode bridge in each of the circuits, and the angle between the magnetic field vectors of the circuits in some cases can be changed to straight (for details, those interested can refer to the original source - description patent).
For example, according to the Certificate of Conformity of the Ministry of Defense of the Russian Federation, series 2 C-994 devices meet the special requirements for devices for destroying information on magnetic media with the orientation of the magnetic induction vector, the erasing magnetic field longitudinally carrier plane. Meanwhile, we are well aware that hard drives with perpendicular magnetic recording have already begun to come into use, where in order to erase information it will be necessary to apply a different magnetic field vector. I wonder if “Surf” will be adapted for these new discs, indicating the new specifics of application? Or the user himself will have to figure out that it is better not to use new disks with perpendicular magnetic recording as “emergency destruction” for storing especially important information? ;)
Unfortunately, at the moment we have not been able to check how reliably Priboy works with hard drives using the new perpendicular magnetic recording - due to the lack of samples suitable for this purpose. :) Let's hope that we can do this in the near future. In the meantime, we tested Surf in detail on traditional three-inch hard drives with longitudinal magnetic recording.
Tests
The shredder testing process takes just seconds. :) Although preparing the tests took a lot of time.
As you already understand, the unit is actually powered from a 220 volt network (by the way, this is why it is strongly recommended to power it from a source uninterruptible power supply, which in case of an emergency will provide enough time to destroy your data). When connected to the network, the LED on the shredder's remote strip (located on the back panel of the computer case) begins to blink red. 
This means that the shredder comes into operating mode, which is established in less than a minute, as indicated by several short sound signals and changing the LED to constant green. 
Now the block is ready to perform the functions of your hard drive Terminator. :)
Execution can be carried out both in direct contact (by pressing a button on the remote control of the shredder) and non-contactly - using a radio remote control, which, according to the manufacturer, operates at a distance of up to 100 meters. To receive a radio signal, a small plastic block with a 15-centimeter antenna wire and an LED that flashes when you press buttons on the remote control is used. To avoid accidental operation, the order of pressing the buttons to activate the destroyer is non-trivial: first you should press the large button (at the same time the “Surf” block begins to beep constantly), and then press the other three buttons in sequence. 
When the shredder is triggered, one very loud mechanical shock is heard (causing a short magnetic pulse), after which the device begins to beep intermittently and blink with a green LED until it is turned off from the network. In this case, the hard drive can be connected to a working computer and even work on its own - the computer will not be harmed (tested personally), although after the shredder is triggered, the disk begins to click its heads madly, trying to find at least some information on the plates, and the operating system, if it was loaded from this drive and used a swap file on it, of course, it will hang.
This file (100 seconds, 500 KB) records the sounds of the destroyer from the moment it is plugged into the network, the readiness signal, the pulse-click, and until the squeal of the dead hard drive. :)
So what happens to the disk itself? We launch, for example, the Victoria program (a more advanced analogue of the popular MHDD) and see that everything that needed to be read from magnetic plates can no longer be read, including the model name, serial number, storage capacity and configuration (manufacturer, name series and the old firmware version number is still read - this time from the drive controller board). 
The drive in the Victoria program before destruction
Of course, there is no information about pre-existing partitions on the disk. Moreover, the information on the disk (sectors) cannot be read even by such low-level programs as, for example, MHDD and Victoria, since they do not see any sectors on it (for example, there is no LBA and CHS addressing, and, apparently, all the service and even servo partitioning are lost ). 
Obviously, the disk is not visible in BIOS Setup host controller (and motherboard). Using a controller board will not save you from having the exact same but working hard drive.
It is clear that in our test laboratory we do not have all the rich professional capabilities for data recovery from magnetic media. It would be optimal, of course, to go with the destroyed hard drives to the special “secret department” of FAPSI (which is now called differently) and “out of former friendship” (which some people still stubbornly suspect us of;)) ask to check how well everything was erased (“it got nailed”). And issue a written opinion on this matter. :) However, we did not distract such serious specialists with our nonsense, especially since similar tests and conclusions on “Priboy” had already been carried out and received - by the manufacturer itself, see certificates above. We did it simpler - we took the disks to well-known private (commercial) domestic laboratories for data recovery from hard drives (we tried to choose some of the best) and under the usual pretext (that is, without introducing them to our research) they offered to recover data from the damaged screws. I think you already guessed the answer - they didn’t manage to do anything! (And with what obscenities they scratched their turnips about the complete unreadability of the service and servo markings with working mechanics and electronics, I think you can also imagine... :) We ask them to forgive us for this. ;))
We sorted out one disk. What happens to objects nearby during this magnetic pulse? To do this, I conducted tests by placing the hard drives close to the sides of the shredder, as well as directly below it - after all, in a real system unit, another disk can be located in a three-inch bay or mobile rack directly under the “terminator”... 
The check showed that the hard drive located directly under the shredder was not damaged at all - the information on it was readable without any difficulty in normal Windows Explorer, and a byte-by-byte comparison of the contents of the sectors before and after the execution of its “upper” neighbor showed a complete match of the records. Moreover, the disks placed close to the sides of the destruction device were not damaged.
The next experiment was to try to fry a “sandwich” - that is, when the second disk is located directly on top of the main one being destroyed. Indeed, in a real system, for example, a mobile rack with a hard drive may be directly above the shredder in the system unit. 
The check showed that the disk that serves as a “caviar”, that is, placed on top of the first one to be destroyed, remains completely intact, no matter which side (up or down) it lies (we are talking about disks of the standard form factor for this thickness 25.4 mm).
Moreover, I conducted another experiment by placing the destroyed hard drive in the Priboi not with the board up (as required), but with the board down. 
After the first magnetic pulse, this disk remained safe and sound! And the information on it was not damaged. However, after the second “shot” of the magnetic pulse working A (simply rotating) drive suddenly had its controller burn out - the ill-fated (for the DiamondMax Plus 9 series) Smooth L7250E driver, as well as the on-board voltage converter regulator chip, were charred. 
Perhaps the reason for this was the Moscow heat and overheating of the already hot cases of these two microcircuits. However, replacing the controller of this disk with a similar working one showed that the information on the disk was intact again! The impulse was repeated on the restored hard drive (with a new controller, already cooled). And the controller burned out again (this time only Smooth was charred and smoking)! However, the next replacement of the controller with a working one showed that this time the information on the disk was not destroyed! Finally, the disk was turned upside down (as required for destruction) and the impulse was repeated (again with the hard drive rotating): this time, everything fell into place - the information on the disk was safely destroyed, and the controller was not damaged and was successfully returned to a working disk from which it was removed for experiments. Thus, for proper operation (as well as fire safety and integrity of the hard drive electronics), a disk with destroyed information Necessarily it should be placed on the “Surf” with the controller facing up, as shown at the beginning of the article. But a hard drive accidentally located above the one being destroyed, in principle, is in virtually no danger, and the information on it should not be damaged by a magnetic pulse from the Priboy.
Honestly, in connection with the latest experiment, the question may arise: how reliably will information be destroyed on modern hard drives, which have, say, 4-5 magnetic plates, some of which are much closer to the controller than to the top roof of the disk? Apparently, on the plates closest to the “Priboy” everything will be OK, but on the plates farther away the power of the magnetic pulse will be noticeably lower, and they may suffer less. Unfortunately, I didn’t have the opportunity to test this position by putting expensive 400-500 GB monsters under the knife, and then trying to read the “distant” plates separately (an experiment on multi-platter disks of the last century, small in size in modern times, I think , is not relevant in this case).
Of course, the magnetic impulse of Priboy can act not only on hard drives, but also on other magnetic media. So, if instead of a hard drive you put a regular floppy disk, then there will be nothing left on it. :) Which was immediately checked. Moreover, if the floppy disks are located on top, bottom or side of the shredder (see photo), 
then nothing happens to the information on them (which once again confirms the “short-range action” of the destroyer’s magnetic field). By the way, unlike a hard drive, a floppy disk can be easily reformatted after such a complete erasure (for example, under DOS). I even managed to recover several previously non-working floppy disks this way. ;)
Conclusion
So, tests confirm that the patented device for emergency destruction of information from magnetic media “Priboy” (2C-994), produced by domestic craftsmen and used in domestic personal computers IRBIS from K-Systems (and, apparently, some others), copes with its responsibilities and “nails” the information on the hard drive to the level of complete unreadability. The device has a fairly well-thought-out and convenient functionality with its own power supply (although a built-in battery would not be superfluous) and the possibility of both contact and remote (up to 100 m) emergency data deletion. Apparently, some small points could be improved (for example, making the mechanical kill button on the rear panel not so easily accessible, adding a battery, reducing the dimensions, etc.). And even think about improvements (for example, especially important data is increasingly stored on RAID 1 arrays, and one “Surf” will not yet be able to destroy both disks at the same time). But in general, devices of this class can turn out to be very useful in a number of cases and will add attractiveness to personal computers designed to work with information that constitutes a certain secret.
We thank the company "" for providing the Priboy shredder for testing and personally Sergei Davydov (Maxtor) for providing hard drives for destruction :)
Long-term storage of user information is provided by an external storage device (ESD). TO external memory include: hard magnetic disk drives (HDD), floppy magnetic disk drives (FMD), magneto-optical compact disk drives, optical disks, magnetic tape drives, etc.
The principle of changing the magnetic induction of the carrier is used in drives of the “ Winchester"(HDD). Hard drives are designed for permanent storage of information used when working with a computer: operating system programs, frequently used software packages, document editors, etc. (Fig. 6).
Rice. 6. HDD.
The main parameters of a hard drive (hard drive) are: disk capacity, number of surfaces, spindle speed, built-in cache memory, interface.
Disk capacity . For the user, hard disk drives differ from each other primarily in their capacity, i.e. how much information fits on the disk. Nowadays, computers are mostly equipped with hard drives of 80 GB or more.
Information on magnetic disks is recorded along concentric tracks and sectors that are formed on the disk as a result of the formatting operation.
The first mainframe computers and even the first personal computers functioned without a hard drive. In modern control computers, programs can be “hardwired” directly into the circuits, and such computers operate without hard drives.
USB flash drives (flash cards) use electronic non-volatile rewritable memory. Flash memory is built on semiconductor elements. Its variety based on cells with NAND elements (NAND) has the highest density and performance.
Streamer (from the English streamer), also a tape drive - a storage device based on the principle of magnetic recording on a tape medium, with sequential access to data (Fig. 7); The operating principle is similar to a household tape recorder.
Rice. 7. Streamer and cartridge for it.
CD Reader designed for reading records on CDs. The advantages of the device are large disk capacity, fast access, reliability, versatility, low cost. The main concept characterizing the work of this device, - speed. Main disadvantage– impossibility of recording information. This requires other devices.
An optical disk with indelible information intended only to be read repeatedly by the user is a CD-ROM ( Compact Disk – Read Only Memory). A CD-ROM drive is commonly used to store commercial programs and data. You cannot add or erase data on a CD-ROM.
To optical DVD-R discs and CD-R, a user can write files more than once (each write is called a session), but files cannot be erased from the disk. Each entry is permanent. Recording on these discs is carried out due to the presence of a special photosensitive layer on them, which burns out under the influence of a high-temperature laser beam.
You can burn files to a CD-RW disc multiple times. You can also delete unnecessary files from the disk to free up space and write additional files. CD-RW disc Can be written and erased repeatedly.
Rice. 8. Optical disc (CD or DVD).
One of the main parameters of any type of computer memory is the memory access time, which is defined as the minimum time sufficient to accommodate a unit of information in memory. The performance of the information storage device is the speed of reading and writing data in the storage device. It is characterized by two parameters: average access time and data transfer rate.
Direct Memory Access (DMA) – a mode of data exchange between devices or between a device and main memory (RAM) without participation central processor(CPU).
Presentation on the topic: Magnetic principle of recording/reading information
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Presentation on the topic:
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Magnetic principle of recording and reading information For long-term storage of information, its accumulation and transmission from generation to generation, material information carriers are used. The material nature of information carriers can be different: DNA molecules that store genetic information; paper on which texts and images are stored; magnetic tape on which audio information is stored; photographic and film films on which graphic information is stored; memory chips, magnetic and laser disks on which programs and data are stored in a computer, etc.
Slide no. 3
Slide description:
Writing/reading information In the process of writing information to floppy and hard magnetic disks, the drive head with a core made of soft magnetic material (low residual magnetization) moves along the magnetic layer of the hard magnetic medium (high residual magnetization). During the process of recording information, sequences of electrical pulses (sequences of logical ones and zeros) are sent to the magnetic head, which create a magnetic field in the head. As a result, the elements of the surface of the carrier are sequentially magnetized (logical one) or not magnetized (logical zero). When reading information, on the contrary, magnetized areas of the carrier cause current pulses in the magnetic head (the phenomenon of electromagnetic induction). Sequences of such pulses are transmitted along the highway to RAM computer.
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Hard magnetic disks Hard magnetic disk drive, HDD, hard drive, hard disk, HDD, HMDD or hard drive, (English Hard (Magnetic) Disk Drive, HDD, HMDD) is a non-volatile, rewritable computer storage device. It is the main data storage device in almost all modern computers. Unlike a “floppy” disk (floppy disk), information in a hard disk drive is recorded on hard (aluminum or glass) plates coated with a layer of ferromagnetic material, most often chromium dioxide.
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Characteristics Capacity - the amount of data that can be stored by the drive. Capacity modern devices reaches 2000 GB. Physical size (form factor) - almost all modern (2002-2008) drives for personal computers and servers are either 3.5 or 2.5 inches in size. Random access time is the time during which the hard drive is guaranteed to perform a read or write operation on any part of the magnetic disk. Spindle speed is the number of spindle revolutions per minute. Reliability is defined as the mean time between failures. The number of I/O operations per second - for modern disks this is about 50 op./sec with random access to the drive and about 100 op./sec with sequential access.
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Characteristics Energy consumption is an important factor for mobile devices. Noise level - the noise produced by the mechanics of the drive during its operation. Shock resistance (eng. G-shock rating) - the drive’s resistance to sudden pressure surges or shocks, measured in units of permissible overload in the on and off state. Data transfer rate (English Transfer Rate): Internal disk zone: from 44.2 to 74.5 MB/s External disk zone: from 60.0 to 111.4 MB/s Buffer volume: A buffer is intermediate memory intended for smoothing out differences in read/write and transfer speeds across the interface.
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The hard drive consists of the following main components: a case made of durable alloy, the actual hard drives (plates) with a magnetic coating, a head unit with a positioning device, an electric spindle drive and an electronics unit. The head positioning device consists of a stationary pair of strong, usually neodymium, permanent magnets and a coil on a movable head block. Contrary to popular belief, hard drives are not sealed. The internal cavity of the hard drive communicates with the atmosphere through a filter capable of trapping very small (several microns) particles. This is necessary to maintain constant pressure inside the disk when the temperature of the case fluctuates.
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Operating principle: The operating principle of hard drives is similar to that of tape recorders. The working surface of the disk moves relative to the read head (for example, in the form of an inductor with a gap in the magnetic circuit). When an alternating electric current is supplied (during recording) to the head coil, the resulting alternating magnetic field from the head gap affects the ferromagnet of the disk surface and changes the direction of the domain magnetization vector depending on the signal strength. During reading, the movement of domains at the head gap leads to a change in the magnetic flux in the head magnetic circuit, which leads to the appearance of an alternating electrical signal in the coil due to the effect of electromagnetic induction.
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Slide description:
Plastic floppy disks The first floppy disks were flexible plastic disks with a diameter of 8 inches, coated with iron oxide and placed in a protective shell, to which a special cloth was glued to the inside, which cleaned the surface of the disk as it rotated. These long-obsolete drives were released by IBM in 1971 specifically for computers with operating system System 370. Indeed, colored squares of plastic with a side of 3.5 inches (which is what most modern floppy disks look like) at first glance have nothing to do with their name, but it should be remembered that this term denotes an item that has been produced for many years ago, and now has long been hidden from view and placed in a plastic case. The first floppy disks were flexible plastic disks with a diameter of 8 inches.
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As computers became more compact, so did disk drives. The 5.25-inch floppy disk was introduced in 1976. They say that its dimensions correspond to the size of cocktail napkins used by the developers who discussed the details of the new project in one of the Boston bars. Today, the most popular floppy disks with a diameter of 3.5 inches, released by Sony Corporation in 1981. Although they are no longer used for transferring files from one computer to another, most machines are still equipped with bays to accommodate these small drives. As a result, some wise (or, conversely, crazy) users still continue to copy the contents of their hard drives to floppy disks.
Logical device Information is recorded along concentric tracks (tracks), which are divided into sectors. The number of tracks and sectors depends on the type and format of the floppy disk. A sector stores the minimum amount of information that can be written to or read from disk. The sector capacity is constant and amounts to 512 bytes.
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Operating principle The floppy disk is installed in a floppy-disk drive, automatically fixed in it, after which the drive mechanism spins up to a rotation speed of 360 min-1. The floppy disk itself rotates in the drive, the magnetic heads remain motionless. The floppy disk rotates only when it is accessed. The drive is connected to the processor through a floppy disk controller.
1.3 Magnetic storage
Classification and main characteristics of drives. Devices that differ in the type of media, the method of registration and the nature of the use of information, the method of access, etc. are used as VSD.
Based on the type of carrier, a distinction is made between VSDs with movable and stationary carriers. If the search, recording and reading of information is accompanied by mechanical movement of the media, then such VSDs are called drives with movable media (magnetic disk drives NMD), optical disks (ODD), magnetic tapes (NMT). If no mechanical movement occurs during searching, writing, or reading, then the VSD is a drive with a stationary carrier (drives based on cylindrical magnetic domains - CMD). Less commonly, volumetric recording is used in VSDs - semiconductor memories, charge-coupled devices.
Based on the recording method, a distinction is made between VCDs with magnetic and optical (magneto-optical) recording.
By the nature of the use of information - permanent memory devices, which allow only reading information, memory devices with a single write (after which only read) and multiple writes (an arbitrary number of records and reads).
According to the method of accessing information - drives with sequential and direct access.
The VZU is usually characterized by the following parameters:
− memory capacity;
− throughput or read-write speed;
− access time, i.e. the time interval from the moment of the request to the moment the block is issued.
VSD recording density b. Here we understand the number of bits of information recorded on a unit of media surface; This surface density. There are also longitudinal density bl, bit/mm, i.e. the number of bits per unit length of media along the velocity vector, and cross density bq, bit/mm, i.e. the number of bits per unit length of media in the direction perpendicular to the velocity vector.
The recording density determines the geometric dimensions of the drive, its performance parameters, and memory capacity.
The principle of recording information on a magnetic surface. As a storage medium, magnetic recording devices use powder and galvanic coatings applied to a non-magnetic medium - a substrate. Dacron is used as a substrate for magnetic tapes. The recording/reading method in NML is contact, the magnetic head is in mechanical contact with the magnetic carrier.
Magnetic disks and drums are coated with metal coatings based on nickel, cobalt, tungsten, applied by electroplating. The thickness of the coating ranges from 0.01 to 1 micron.
Flexible magnetic disks (floppy disks) are cut out of magnetic film. Floppy magnetic disk drives (FMD) also use the contact method, in contrast to hard magnetic disk drives (HDD) and hard drives, where the write-read method is non-contact.
To magnetize individual sections of the magnetic coating for the purpose of recording, a magnetic head or a block of magnetic heads is used, consisting of a magnetic core with a gap and an inductor coil wound on it.
Floppy disk drives. The device (NGMD) (Figure 1.19) includes a GMD, five main systems (drive mechanism, positioning mechanism, centering and fastening mechanism, control and monitoring system, recording-reading system) and three special sensors (index hole sensor, write prohibition sensor, sensor track 00).
The usable surface of the disk is a set of tracks located at a certain pitch. Track numbering starts from the outside (track zero). The position of track 00 is determined in the drive using a special photoelectric sensor. The track itself is divided into separate recording sections of equal length - sectors. The beginning of the read-write sections on the tracks is determined by a special round index hole on the disk. When the index hole passes under the corresponding window of the cassette as the disc rotates, another photoelectric sensor generates a short electrical pulse, which detects the position of the beginning of the track.
In HDMI, two main recording methods are used: the frequency modulation (FM) method and the modified FM method.
Floppy disk drive adapters. The HDD adapter translates commands coming from the BIOS ROM into electrical signals, controlling the float drive, and also converts the flow of pulses read from the floppy disk into information perceived by the PC. Structurally, the electronic equipment of the adapter can be placed on the system board. One of the options for constructing a block diagram of a flat-foot drive adapter is shown in Figure 1.20.
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The main functional block of the float drive adapter is the float drive controller, which is usually implemented structurally in the form of a LSI (integrated circuits 8272 Intel, 765 NEC, etc.). This controller provides control of the operations of the float and determines the conditions of exchange with the central processor.
The float drive controller performs the following set of commands: positioning, formatting, reading, writing, checking the float drive status, etc. Each command is executed in three phases: preparatory, execution and final.
Zip drives.Zip drives are available in internal SCSI and ATAPI models and external devices, connected via a parallel port or SCSI and USB interfaces. Zip disks have a maximum capacity of 250 MB (supported by all drives except the USB model). Maximum speed The exchange rate of the first Zip models reached 1.4 MB/s, with an average access time of about 30 ms. The new models are a little faster. According to their own speed characteristics They are comparable to, say, modern CD-RW drives, slightly inferior in read speed and disk access time, but superior in write speed.
Another option for removable drives based on the use of soft magnetic disks is the so-called floptic technology. This solution implies that the positioning of the read/write head is carried out using a laser beam on the service track (servo-track), and the read and write operations themselves are carried out using a standard magnetic method.
Modern devices have a data transfer speed of 1.1 MB/s (ATAPI). For SCSI drives this figure is even higher - up to 4 MB.
Streamers.They are used for archiving or backup purposes because they use magnetic tape as the storage medium. (lavsan, polyester or acetate film), coated with ferrolacquer applied in a magnetic field to orient flat domains along the axis of easy magnetization.
Depending on the type of drive and, accordingly, the media, tapes of different widths and lengths are used, ranging from 3.61 mm for mini-cassettes to 35 mm for reels (reels). The most commonly used tape is 12.7 mm wide; With a larger width, tape distortions occur and the block of magnetic heads becomes more complicated. The placement of information depends on the width of the tape. On narrow tapes, information is recorded in a serial code, on wide tapes - in parallel. Recording in parallel-serial code is also used.
Figure 1.21 shows the placement of information on the ML during serial-parallel recording on 11 tracks. Each track has its own magnetic head: 8 information heads, a sync pulse head, and a zone start head.The greatest amount of time is spent searching for a zone - it can reach several minutes depending on the location of the desired zone on the tape. Tape transport mechanisms ensure the advancement of the tape at speeds from 0.9 to 6.3 m/s. and information exchange speed from 30 KB/s to 1.5 MB/s. To ensure quick start and stop of the tape, the NML tape transport mechanism has vacuum columns, which are buffer devices containing a certain supply of tape in the form of a compensation loop.
A) placement of zones of arbitrary length on the tape;
b) placement of information in the zone
Figure 1.21 - Placement of information in the serial-parallel form of information placement on NML magnetic tape
NML controllers perform the functions of controlling the operating modes of the drive according to commands received from the computer. NML controllers are standardized and allow you to connect up to 8 drives different types in any combination to the computer channel.
NMLs are connected to the controller using a standard interface. The most commonly used are 8 control buses, 4 status flag buses and 8 response buses. Control buses and feature buses are common to all NMLs connected to the controller.
Optical and magneto-optical storage devices. Optical external memory devices have a high density of information recording, several orders of magnitude greater than the density of magnetic memory devices, since to register one bit, a section on the medium with dimensions on the order of the wavelength of laser-emitted light (about 0.5 microns) is sufficient. This type of external memory has high performance and reliability.
Both recording on an optical medium - an optical disk, and playback from it are carried out with a laser beam. Lasers are capable of generating and amplifying electromagnetic oscillations in the ranges of 0.4 mm...0.78 microns (infrared part of the optical spectrum, these are masers), 0.78...0.38 microns (visible light waves) and 0.38. ..2 nm (ultraviolet part of the spectrum).
A digital optical disk consists of a working (recording, information) layer, onto which an information signalgram is applied in the form of certain alternations of its states, and a base on which this working layer is located. Figure 1.22 shows the design of a Philips double-sided CD, which has two transparent foundations with the working layers are connected together and form a closed space for the working layers.
Figure 1.22 - Design of a double-sided optical disk
There is a reflective mirror layer and an air gap. The backing is made of plastic. Tellurium and its alloys, an alloy of selenium, indium, copper, aluminum, nickel and zinc are used as the material of the working layer.
The design of the optical head intended for writing and reading disks is shown in Figure 1.23. The most common CDs are 119 mm (4.7 inches) in diameter. A write-once disk of this diameter contains 550 or 680 MB. Disks with a diameter of 80 mm and a capacity of 200 MB are also produced.
Figure 1.23 - Combined type optical head for rewritable discs
Recording devices operate in three modes. In single-session mode, the entire disc must be written in one pass without interruption. Multi-session mode allows you to record data over several sessions, resulting in the information on the disk being presented in the form of separate volumes, reminiscent of logical partitions hard drive and incremental mode allows you to record part of the data, stop, and then continue recording.
An optical disk OSD consists of two parts: an optical disk drive (ODS) and a control device (CU), shown in Figure 1.24.
Figure 1.24 - Generalized block diagram of an optical disk OSD
The drive carries out the processes of recording, storing, reading, erasing and retrieving information.
Relationship between control unit and GCDcarried out via buses: commands, status, addresses and along lines: recording data, playback data, synchronization of playback data.
Recording channel- playback (KZV) is part of the information channel of the VZU on the OD. With its help, recording and playback of information on the OD is realized. It consists of an optical and electrical part. The optical part of the channel is called the optical head (OG).
Electrical part of the KZV during the recording process, converts information signals coming from the controller into a form suitable for recording on the OD, and directly controls the implementation of the recording process by changing the intensity of the laser beam incident on the OD recording point in accordance with the information signals. During playback, the electrical part of the KZV processes electrical signals coming from the photodetector: it generates, detects, recognizes and transmits them to the controller.
High-speed MO drives use a large buffer cache memory (from 4 MB) in write and read modes.
The information retrieval system in a GCD includes an optical head positioner, an OD drive and, in the case of multi-disk GCDs, a system for storing, selecting and changing ODs.
The OG positioner is used to move the OG to a given OD track and hold the light beam on the track during recording and playback.
Figure 1.25 shows the block diagram of a CD ROM.
Figure 1.25 - Structural scheme CD-ROM
Compound:
- servo disk rotation control system;
- Servo positioning system for laser reading device;
- servo autofocus system;
- radial tracking servo system;
- reading system;
- laser diode control circuit.
The servo disk rotation control system ensures the constant linear speed of the reading track on the disk relative to the laser spot. Characteristic features proper operation there are clearly visible phases:
– start and acceleration of disk rotation;
– steady state of rotation;
– braking interval to a complete stop;
– remove the disc using the carriage tray and take it out of the drive.
Figure 1.26 shows the structure of connections of the optical-electronic information reading system.
Figure 1.26 - Structure of connections of the optical-electronic system
reading information
The servo system for positioning the information reading head ensures a smooth approach of the head to a given recording track with an error not exceeding half the track width in the search modes for the required piece of information and normal playback. The radial tracking servo system ensures that the laser beam remains on the track and provides optimal conditions for reading information.
Monitoring and control of the vertical movement of the focusing lens is carried out under the influence of servofocus. This system ensures precise focusing of the laser beam while working on the working surface of the disk.
The information reading system contains a photodetector matrix and differential signal amplifiers. The normal operation of this system can be judged by the presence of high-frequency signals at its output when the disk rotates.
The laser diode control system provides the rated excitation current of the diode in the disk starting and information reading modes. Sign normal operation system is the presence of an RF signal with an amplitude of about 1 V at the output of the reading system.
VZU on CMD-containing materials. Cylindrical magnetic domains (CMDs) are isolated uniformly magnetized regions of a magnet in the form of circular cylinders, the direction of the magnetization vector in which is opposite to the direction of magnetization of the rest of the magnet.
To create CMDs, in practice, thin plane-parallel plates are used on a substrate - films (thickness from 1 to 100 microns) of magnetic materials with anisotropy induced during the manufacturing process, which have a low residual induction of the order of 0.01 - 0.02 tesla.
VZU based on holography. The use of laser technology to input, store and output information in the form of three-dimensional images has made it possible to create holographic display media (SD). The memory capacity of holographic memories is practically unlimited: the theoretically achievable recording density using two-dimensional holograms is 410 8 bits/cm2, and using volumetric holograms - 41012 bits/cm 3 .
