Hard drive diagnostic software:Seagate Seatools

Seagate creates two free hard drive diagnostic softwares – SeaTools for DOS and SeaTools for Windows. Both diagnostic tools are excellent.

1. SeaTools for Windows
SeaTools for Windows has replaced SeaTools Online and PowerMax. SeaTools for Windows is a comprehensive, easy-to-use diagnostic tool that helps you quickly determine the condition of the disc drive in your external hard drive, desktop or notebook computer. It includes several tests that will examine the physical media on your Seagate or Maxtor disc drive and any other non-Seagate disc drive.

SeaTools for Windows tests USB, 1394, ATA (PATA/IDE), SATA and SCSI drives. It installs onto your system. SeaTools for Windows is completely data safe.

User Guide about SeaTools for Windows.
Download SeaTools for Windows

2. SeaTools for DOS
SeaTools for DOS has replaced SeaTools Desktop and PowerMax. SeaTools for DOS can test Seagate or Maxtor Parallel ATA (PATA and IDE) and Serial ATA (SATA) interface disc drives. Because the software boots to its own operating system you can test your drive regardless of the OS installed on it.  You can even test a new or completely blank drive.  SeaTools for DOS will instruct the drive to run its built in Drive Self Test (DST) and give either a pass or fail status.  If you are troubleshooting your disc drive and the DST passes, then you have a good drive!

User Guide about SeaTools for DOS.
See the tutorial on the usage of SeaTools for DOS.
Download SeaTools for DOS

Pros
• Two versions are available depending on needs
• Both versions are easy to use once installed and are completely FREE
• SeaTools for Windows tests hard drives no matter the manufacturer
• SeaTools for DOS contains a highly useful “acoustic test” for noise troubleshooting
• SeaTools for DOS is OS independent so it’s automatically compatible with ALL operating systems

Cons
•  SeaTools for DOS requires ISO image burner software that novice users may have difficulty using
•  SeaTools for DOS handles a maximum of only 100 errors, at which point testing has to begin again

Description
• Seagate SeaTools is available in both a Windows version and a stand-alone, bootable version for maximum flexibility.
• Tests in both SeaTools versions are easy to understand and run.
• SeaTools for Windows can test all types of internal drives including SCSI, PATA, SATA, etc.
• SeaTools for Windows can also test external drives like those based on the USB or FireWire standards.
•SeaTools for DOS features an Acoustic Test to help you determine if a noise is from your hard drive or another component.

3. Guide Review – Seagate SeaTools
Seagate’s SeaTools hard drive testing programs are some of the easiest to use of any I’ve ever worked with. The test are basic, easy to run, and generally pretty fast in my tests.

The SeaTools hard drive testing software comes in two different versions. SeaTools for Windows runs on Windows 2000, XP or Vista. SeaTools for DOS runs outside of the operating system so the tool will work on your PC no matter what OS you use.

SeaTools for Windows can perform several basic tests that can help determine the health of your hard drive. Your available hard drives and tests are easy to see when the program opens and can be ran with just a few clicks of the mouse.

You can test hard drives from any manufacturer and of any type, including PATA, SATA, and SCSI internal drives along with USB and FireWire external drives. To begin, simply download the software from Seagate’s site and install in Windows.

SeaTools for DOS can also perform the several basic tests that SeaTools fro Windows can run but it can also run a very useful Acoustic Test. This test can really save you a lot of time during the troubleshooting of a noisy internal component. It will spin the drive down until it’s completely idle, making the drive nearly silent. If you no longer hear the strange noise, the hard drive was the culprit!

With SeaTools for DOS, you can only test hard drives from Seagate and Maxtor. To begin, download either the Floppy Diskette Creator to make a bootable floppy disk (this is the easier option) or the ISO CD-ROM Image to burn to a CD. If you need help burning the CD, check out How to Burn an ISO Image File to a CD or DVD.

So if you’re comfortable burning ISO images and you want a slightly more powerful test, use SeaTools for DOS. If you’re more of a novice or you just want a quick and basic hard drive test, give SeaTools for Windows a try.

Both softwares are completely free and I highly recommend them. If you suspect that your hard drive may be failing, one or both of these tools from Seagate will help you determine what’s wrong.

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The advantages of USB Flash Drive

USB Flash DriveA USB flash drive is a NAND type flash memory. The NAND type flash memory was designed for the exchange and saving of data as alternative to the magnetic disk. The NAND type flash memory has the capacity to hold large volumes of data. The writing and erasing speed is also fast. The USB drive can be easily inserted into the USB port of the computer. With the help of USB flash drive, data can be safely and easily transferred. The USB drive is more reliable and safer than the floppy disks. The USB drives are small and compact.

A USB flash drive is a NAND type flash memory. The NAND type flash memory was designed for the exchange and saving of data as alternative to the magnetic disk. The NAND type flash memory has the capacity to hold large volumes of data. The writing and erasing speed is also fast. On the other hand the random access is rather slow because it uses block as a unit for the purpose of writing and reading.

The USB drive is made up of secure case small circuit board and is integrated with a universal serial bus connector. The secure case is typically made up of rubber or metal. This secure case protects the circuit board of the USB drive from damage and increases the robustness. The USB drives are very much smaller than the floppy disks and are rewritable.

The USB drive can be easily inserted into the USB port of the computer. With the help of USB flash drive, data can be safely and easily transferred. The USB drive is more reliable and safer than the floppy disks. The USB drives are small and compact, therefore the users can carry them easily in their pockets or they can attach it with their key chains as well.

The USB drives are more reliable when huge amounts of data has to be moved. Some of the USB drives allow 1 million erase or write cycles. The USB Memory card readers have a removable flash memory card. The USB flash drives provide more benefits to its users than the other storage devices. Almost all the computers and laptops have the USB ports, therefore the users can easily transfer the data. Most of the modern operating systems have the USB mass storage standard which is required by the USB flash drives to operate.

The USB 2.0 are much faster than the optical disk in terms of the data storage in much smaller space. The name “drive” is given to the USB flash drive because the USB flash appears to the OS of the computer like a mechanical drive and the method of access is also the same.

The USB connector must be protected and kept safe using a removable cap or by retracting the USB connector into the body of the USB flash drive. The USB flash drives use all the power supply from the host connection. Some high speed USB drives may require more power supply than provided by the bus powered USB hub. Therefore these drives will function when they are directly plugged into the self powered hub or the host controller.

The USB drives are most often composed of three components, the male connector type A, crystal oscillator and the USB mass storage controller. The function of the type A connector is to interface with the system of the host computer. While on the other hand the USB mass storage controller helps in balancing and storage of the data. The USB mass storage controller enhances and carries out smooth processing of the decoding, encryption and transfer of the data between the systems. The function of the crystal oscillator is to make sure that the output of the flash drive is of the best quality.

The reason that the USB drives became more popular is that the floppy drives were most of the time failed to read the data from the floppy disk. Therefore, the users had problems while transferring the data using the floppy disks. The USB flash drives do not have movable parts like the floppy disks had.

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Simpletech USB External Hard Disk Drive

Simpletech usb external hard disk driveThe external hard drives can be portable and connects to the computer system from external. Cable is used for connecting the external hard drives to computer system; it supports the IDE, SCSI and USB. The other bus standards are also compatible.  For windows operating system, the internal hard drives were used in the computer systems during the last years of the twentieth century. On the other hand the external drives were mostly used on Apple Macintosh during the twentieth century.

The USB SimpleTech external hard disc drive is the best solution to fulfill the high capacity data storage medium for transferring the data. It provides high performance with low cost per gigabyte and therefore, it creates good value and customer satisfaction. The design of the SimpleTech USB external hard disc drive is very stylish and its size is also small. On top of the external drive are 4 Light emitting diodes in the form of a circle, these LED are used as a “capacity meter”.

The 25% of total capacity of the external drive is represented by each of the LED. These Light emitting diodes show the used storage space. When the free storage space is lesser than 10%, then the LEDs flash in red color giving an indication to the user. When copying is being done then the LEDs also flash at that time.

The external USB hard disks gain popularity as the backup storage needs increased with the introduction of the internet. The data was to be protected from threats of viruses and unauthorized usage. Therefore, the use of USB disk drives increased. The design and the internal structure are very much similar of both the internal and the external hard disks and are mounted on disc enclosure.

The Linux, UNIX and Windows all the 3 leading operating systems support the USB external hard disk drives. All these operating systems provide the partitioning and the disc formatting tools for the external hard drives. The Operating system can also be installed on the external drives, in this way the applications and programs can run on the computer. The file systems like the NTFS and FAT can also run on the USB external hard disks. In the Windows2000, Windows Vista and WindowsXP the Disk Management Console tool can be used for the partition and formatting of the USB external hard discs. For UNIX operating system the boot camp and the disk utility can be used for this purpose. And for the Linux operating system, the qtparted or the gparted can be used for formatting and partitioning purpose. The small sized external drives are also known as the “pocket drives”.

The flash drives are smaller in size than the pocket hard disks, but they USB external hard drives can transfer and store huge volumes of data. The data storage capacity of the pocket external drives is about 4GB to 8GB. The pocket USB external hard drive is little bit bigger in size than the USB flash drive. There are built in drivers of the pocket external hard disk drives in the operating systems of modern computers. The SimpleTech USB external hard disc drive has recording capacity of 320GB, 750GB and up to 1 Terabyte.

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HDD Repair And Data Restoration Tool: PC3000 UDMA

1.What is pc3000 UDMA?
PC3000 UDMA is a new product of ACE Laboratory combining a wealth of long experience in data recovery and HDD repair market with 18 years of work with their first products: PC-2000 MFM/RLL, PC-3000 DOS (ISA), and PC-3000 for Windows PCI recognized by data recovery experts worldwide.
PC3000 UDMA
(Specialized two-port tester card PC-3000 UDMA)

2.Which problems can be solved using PC-3000 UDMA?
The features provided by PC-3000 UDMA can be conventionally subdivided into two parts according to their purpose:

  • HDD repair
  • Restoration of user data

Operations with HDD printed circuit board (PCB):

  • Scanning of firmware microcode in ROM; verification of configuration data in ROM; verification of firmware version in ROM; buffer RAM test; performance of self-diagnostics.
  • Reading and recording of Flash ROM containing firmware microcode and configuration data in ROM. The data for programming of Flash ROM can be copied from the resource database of the PC-3000 for Windows (UDMA) suite.

Operations with HDD service area (SA):

  • Testing of service area for BAD sectors; scanning of service modules to detect possibly corrupted sections.
  • Erasure and formatting of service area; restoration of damaged SA modules or their overwriting with standard reference data from the resource database of PC-3000 for Windows (UDMA).

Operations with HDD disks:

  • Surface testing and detection of BAD sectors; launching the internal low-level format procedure.
  • Relocation of revealed surface defects updating the defect tables; launching the Self Test procedure.

Operations with reading/writing HDD heads:

  • Head testing (for some drive families only).
  • Isolation of malfunctioning heads. HDD capacity decreases in such cases but the drive may become completely functional.

Universal features for operations with HDD:

  • An opportunity to reset SMART parameters of a HDD.
  • An opportunity to correct drive identificatin data (ID).
  • An opportunity to unlock USER and MASTER passwords in a HDD.
  • An opportunity to delete HDD data quickly without impeding its functionality.
  • Read data in UDMA66 mode.

3. PC3000 UDMA FAQS:

1. Can users add new factory modes on their own?
Yes, if the user is quite proficient and familiar with programming basics! For this, PC-3000 for Windows (UDMA) suite has:

  • Built-in script engine, which allows independent extension of utility features. Of course, the task may be daunting for novice users, but after some experience someone who has mastered the product perfectly may attempt to enhance its functionality. Open interface of the PC-3000 for Windows (UDMA) suite provides a wide range of opportunities for that purpose. Besides, users of PC-3000 for Windows (UDMA) can exchange the resources and ready scripts for new factory modes.
  • ATA Commander is another tool that allows inspection of new HDD modes. In fact, it offers a real research lab for users who wish to analyze HDD operation on their own. АТА Commander allows you to send to a HDD any command including factory ones. It also supports their classification, reuse and conversion to scripts, if necessary.

2. Does PC-3000 UDMA support 2.5″ and 1.8″ HDDs?
Yes, the package of PC-3000 for Windows (UDMA) includes a special PC-2″ mini ATA adapter for connection of 2.5″ and 1.8″ HDDs to the PC-3000 UDMA tester board. The software portion of the complex includes factory mode utilities for 2.5″ and 1.8″ drives manufactured by IBM, Hitachi, Toshiba, Fujitsu, Seagate, Western Digital, and Samsung.

3. Does PC-3000 for Windows (UDMA) support 1.0″ Microdrive HDDs?
1.0″ HDD are relatively new. They are designed for use in portable devices featuring the Compact Flash interface. PC-3000 for Windows (UDMA) suite includes a special PC-CF adapter with the Compact Flash interface, which allows connection of such drives to the PC-3000 UDMA tester board. A specialised utility for Hitachi 4-16 Gb Microdrives is currently in development.

4. Does PC-3000 for Windows (UDMA) support SATA HDDs?
Yes, the package of PC-3000 for Windows (UDMA) includes a special PC PATA-SATA adapter for connecting SATA HDDs to the PC-3000 UDMA tester board. The software part of the suite includes factory mode utilities for operations with SATA HDD.

5. Can PC-3000 for Windows (UDMA) be used to unlock a password-protected HDD?
Yes, it can. Factory mode utilities feature a special mode for work with the password-based security subsystem of HDDs. The mode allows you to view and erase existing Master and User passwords thus unlocking the HDD. For most 3.5″ and 2.5″ HDD unlocking is based entirely on software methods in factory mode. Some types of 2.5″ HDD require special Unlock 2,3 probes.

4. PC3000 UDMA Case studies:

Case 1. A Western Digital WD1200PB-00FBA0 drive cannot be identified in computer BIOS, we need to recover user data.

In the first place it is necessary to power-up the HDD and listen carefully to check whether the spindle motor spins up and the drive produces recalibration sounds (PC-3000 is not required during that stage). If the spindle motor spins up, check the settings of configuration jumpers, they should set the drive to be Master Only (in WD drives the mode is on when all jumpers are disabled), then you can connect the drive to the PC-3000 UDMA tester board.

That can be accomplished using a flat IDE cable connected to port 0 or 1 and a power cable. Then it is time to run the software (PC-3000 for Windows), power-up the HDD and launch the PC-3000 universal utility.

If the universal utility is unable to read ID from that HDD and reports error 04h (ABRT), then you should launch a specialized utility for Western Digital HDDs. It will switch the drive to factory mode and attempt to read firmware header in ROM and the configuration sector in service area on disk.

If the utility succeeds and outputs drive information to a report on display, then it starts service area structure test taking several minutes. Then the test results will be displayed. They will likely inform about damaged firmware modules 20h, 21h and 25h. The cause of HDD malfunction becomes evident. Using the “service modules” wizard one can tell that the modules belong to drive translator; modules 20h and 25h at that will be able to recover without assistance when the “regenerate translator” procedure is performed, but module 21h has to be overwritten. To do so, you will have to select from the database of the PC-3000 complex for Windows module 21h, having specified model WD1200PB-00FBA0 and firmware version 15.05R15 as search criteria. Use the list of suggestions to pick any module 21h and select the “write to drive” option. Then you will have to select the “regenerate translator” option and the default menu item; the program will also display the “recommended for data recovery” tip. Then switch the drive’s power supply off and on again to make it initialize itself with new parameters and ensure than the drive is functional and user data can be accessed. Now you can connect that HDD to a computer normally and copy necessary data from it.

Case 2. A Fujitsu MHS2020AT is identified normally in computer BIOS, but during the startup procedure you receive a message about HDD malfunction. We need to recover user data from it.

To connect that 2.5″ HDD to your PC-3000 for Windows system, you will have to use the PC-2″ adapter included into the package. Then power-up the HDD and listen carefully to check whether the spindle motor spins up and the drive produces recalibration sounds (PC-3000 is not necessary during that stage). If the spindle motor spins up, then you can connect the drive to the PC-3000 UDMA tester board and launch the PC-3000 universal utility. At the start the latter will attempt to read identification parameters of the HDD and display the information in its report. In that case the utility would read drive description, but it would also output the following message: “WARNING! Security locked drive”. The cause of HDD malfunction becomes evident.

You may not know the password defined for that HDD, so you should start a specialized utility for 2.5″ Fujitsu drives. Then select the “Security disable password” mode from the “Security subsystem” menu of the utility. The operation will take only a couple of seconds and the password will be disabled. Then switch the drive’s power supply off and on again to make it initialize itself with new parameters. Make sure than the drive is functional and user data can be accessed. Now you can connect that HDD to a computer normally and copy necessary data from it.

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SD Memory Cards

SD Memory CardThe SD memory cards known as the “Secure Digital” first began as miniature cards. Afterwards the new and advanced form of the SD memory card SDIO “Secure Digital Input/output” was introduced into the market. The SDA “Secure Digital Association” included new features and technology to the SD memory cards. The SDA included new varieties of card functions. These new card functions included wireless “Local Area Network LAN” devices, cell phones, GPS receiver, digital video camera etc. The memory card readers that were used in the Secure Digital devices connected to the Universal Serial Bus (USB). The Windows Operating System detects and manages the SD (Secure Digital) memory cards through the driver called the (USB) Universal Serial Bus mass storage. The (SD) Secure Digital host controllers are supported by the Operating System. The Operating System connects the host controller SD to the Peripheral Component Interconnect (PCI) bus. When the SD-host controller is detected by the operating system, the “SD Secure Digital bus driver” is loaded by the operating system OS. When the SD card is inserted by the user, the windows Operating system loads two drivers the “Storage mini-port” and the “SD Secure Digital Storage Class”. These two drivers are loaded on top of “Bus driver” by the Windows Operating System. On the other hand if the SD memory card of a different function like the wireless Local Area Network (LAN) or the Global Positioning System is inserted by the user, then the Windows Operating System loads the driver that is supplied by the vendor. It is necessary that both the vendor supplied and the native drivers in the (SD) Secure Digital stack communicate with “Secure Digital Bus”. The device drivers call the routines to communication with the “Secure Digital Bus”. These routines are called in the static “Secure Digital Bus library”. When the SD Secure Digital drivers compile, it is necessary that they link to the “Secure Digital SD Bus library”. There are some limitations for the SD device drivers. The “Host Controller Register” is not directly accessible by the Secure Digital device drivers.

The SD device drivers call the routines of “Secure Digital Library”. Then the Secure Digital Library forwards the Secure Digital commands to “Host Controller”. Music can be stored in the Flash Memory card and it is most advantageous than storing it in the Hard drives.  The SD flash memory cards consume less power and are more portable. The SD flash cards also have resistance to shocks. The SD card facilities its users and they can easily record the data to their personal liking like music, pictures. The users can easily carry and move the data with ease and comfort. The SD memory card has the technology to fulfill the requirements of the future networked society. The tiny SD memory card provides many advantages to their users. These memory cards are highly compatible and they can link to different digital equipments. Because of the compatibility of the SD memory cards, their usage is more likely to expand even more in the future. The SD card has now become a standard of memory cards that are used for digital connectivity. In the near by future, the SD cards will be universally accessible to more wide array of Multimedia data. The size of the SD memory card is approximately 24mm x 32mm x 2.1mm. The design of the SD card is very compact and slim. Therefore, they are easy to handle and the user can easily transfer the data.

The devices that are compatible with SD card can play video clips & music with the help of “decoder software”. The DVD & CD players use “drive mechanism” while the SD memory cards do not require “drive mechanism” to play the video clips. So, this gives the product designers more freedom and they can be more creative and innovative. The other popular form of the SD memory card is the miniSD memory card. The size of the mini-SD card is approximately 20mm x 21.5mm x 1.4mm. The miniSD card is smaller in size than the SD card.

The SD memory cards have different recording capacitates, their capacity reaches up to 8GB. The large capacity helps to store the High quality videos. The demand for high capacity SD cards with fast data transfer speed has increased because of the increased digital content range. The SD cards also have the technology of “Copyright Protection”. This “Copyright Protection” technology enables new distribution system. This provides safety and security to the illegal copying of the data.The SD card has built in technology called the Key Revocation. The SD memory card has “Control Circuit”, which allows to read & write the after the detection of the external devices. The data is written and read within the “protection area” of the card. The authentication among the digital devices has to be enabled so that the SD card could be accessed.

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Data encoding schemes

Magnetic storage is essentially an analog medium. The data a PC stores on it, however, is digital information that is, 1s and 0s. When the drive sends digital information to a magnetic recording head, the head creates magnetic domains on the storage medium with specific polarities corresponding to the positive and negative voltages the drive applies to the head. The flux reversals form the boundaries between the areas of positive and negative polarity that the drive controller uses to encode the digital data onto the analog medium. During a read operation, each flux reversal the drive detects generates a positive or negative pulse that the device uses to reconstruct the original binary data.

To optimize the placement of flux transitions during magnetic storage, the drive passes the raw digital input data through a device called an encoder/decoder (endec), which converts the raw binary information to a waveform designed to optimally place the flux transitions (pulses) on the media. During a read operation, the endec reverses the process and decodes the pulse train back into the original binary data. Over the years, several schemes for encoding data in this manner have been developed; some are better or more efficient than others, which you see later in this section.

Other descriptions of the data encoding process might be much simpler, but they omit the facts that make some of the issues related to hard drive reliability so critical namely, timing. Engineers and designers are constantly pushing the envelope to stuff more and more bits of information into the limited quantity of magnetic flux reversals per inch. What they’ve come up with, essentially, is a design in which the bits of information are decoded not only from the presence or absence of flux reversals, but from the timing between them. The more accurately they can time the reversals, the more information that can be encoded (and subsequently decoded) from that timing information.

In any form of binary signaling, the use of timing is significant. When interpreting a read or write waveform, the timing of each voltage transition event is critical. Timing is what defines a particular bit or transition cell that is, the time window within which the drive is either writing or reading a transition. If the timing is off, a given voltage transition might be recognized at the wrong time as being in a different cell, which would throw the conversion or encoding off, resulting in bits being missed, added, or misinterpreted. To ensure that the timing is precise, the transmitting and receiving devices must be in perfect synchronization. For example, if recording a 0 is done by placing no transition on the disk for a given time period or cell, imagine recording ten 0 bits in a row you would have a long period of ten time periods or cells with no transitions.

Imagine now that the clock on the encoder was slightly off time while reading data as compared to when it was originally written. If it were fast, the encoder might think that during this long stretch of 10 cells with no transitions, only 9 cells had actually elapsed. Or if it were slow, it might think that 11 cells had elapsed instead. In either case, this would result in a read error, meaning the bits that were originally written would not be read as being the same. To prevent timing errors in drive encoding/decoding, perfect synchronization is necessary between the reading and writing processes. This synchronization often is accomplished by adding a separate timing signal, called a clock signal, to the transmission between the two devices. The clock and data signals also can be combined and transmitted as a single signal. Most magnetic data encoding schemes use this type of combination of clock and data signals.

Adding a clock signal to the data ensures that the communicating devices can accurately interpret the individual bit cells. Each bit cell is bounded by two other cells containing the clock transitions. By sending clock information along with the data, the clocks remain in sync, even if the medium contains a long string of identical 0 bits. Unfortunately, the transition cells used solely for timing take up space on the medium that could otherwise be used for data.

Because the number of flux transitions a drive can record in a given space on a particular medium is limited by the physical nature or density of the medium and the head technology, drive engineers have developed various ways of encoding the data by using a minimum number of flux reversals (taking into consideration the fact that some flux reversals used solely for clocking are required). Signal encoding enables the system to make the maximum use of a given drive hardware technology.

Although various encoding schemes have been tried, only a few are popular today. Over the years, these three basic types have been the most popular:

  • Frequency Modulation
  • Modified Frequency Modulation
  • Run Length Limited

FM Encoding
One of the earliest techniques for encoding data for magnetic storage is called Frequency Modulation encoding. This encoding schemesometimes called Single-Density encodingwas used in the earliest floppy disk drives installed in PC systems. The original Osborne portable computer, for example, used these Single-Density floppy disk drives, which stored about 80KB of data on a single disk. Although it was popular until the late 1970s, FM encoding is no longer used.

MFM Encoding
Modified Frequency Modulation encoding was devised to reduce the number of flux reversals used in the original FM encoding scheme and, therefore, to pack more data onto the disk. MFM encoding minimizes the use of clock transitions, leaving more room for the data. It records clock transitions only when a stored 0 bit is preceded by another 0 bit; in all other cases, a clock transition is not required. Because MFM minimizes the use of clock transitions, it can double the clock frequency used by FM encoding, enabling it to store twice as many data bits in the same number of flux transitions.

Because MFM encoding writes twice as many data bits by using the same number of flux reversals as FM, the clock speed of the data is doubled and the drive actually sees the same number of total flux reversals as with FM. This means a drive using MFM encoding reads and writes data at twice the speed of FM, even though the drive sees the flux reversals arriving at the same frequency as in FM.

Because it is twice as efficient as FM encoding, MFM encoding also has been called Double-Density recording. MFM is used in virtually all PC floppy disk drives today and was used in nearly all PC hard disks for a number of years. Today, virtually all hard disks use variations of RLL encoding, which provides even greater efficiency than MFM.

MFM Data-to-Flux Transition Encoding

RLL Encoding
Today’s most popular encoding scheme for hard disks, called Run Length Limited, packs up to twice the information on a given disk than MFM does and three times as much information as FM. In RLL encoding, the drive combines groups of bits into a unit to generate specific patterns of flux reversals. By combining the clock and data signals in these patterns, the clock rate can be further increased while maintaining the same basic distance between the flux transitions on the storage medium.

IBM invented RLL encoding and first used the method in many of its mainframe disk drives. During the late 1980s, the PC hard disk industry began using RLL encoding schemes to increase the storage capabilities of PC hard disks. Today, virtually every drive on the market uses some form of RLL encoding.

Instead of encoding a single bit, RLL typically encodes a group of data bits at a time. The term Run Length Limited is derived from the two primary specifications of these codes, which are the minimum number (the run length) and maximum number (the run limit) of transition cells allowed between two actual flux transitions. Several variations of the scheme are achieved by changing the length and limit parameters, but only two have achieved any real popularity: RLL 2,7 and RLL 1,7.

You can even express FM and MFM encoding as a form of RLL. FM can be called RLL 0,1 because as few as zero and as many as one transition cells separate two flux transitions. MFM can be called RLL 1,3 because as few as one and as many as three transition cells separate two flux transitions. (Although these codes can be expressed as variations of RLL form, it is not common to do so.)

RLL 2,7 was initially the most popular RLL variation because it offers a high-density ratio with a transition detection window that is the same relative size as that in MFM. This method provides high storage density and fairly good reliability. In very high-capacity drives, however, RLL 2,7 did not prove to be reliable enough. Most of today’s highest capacity drives use RLL 1,7 encoding, which offers a density ratio 1.27 times that of MFM and a larger transition detection window relative to MFM. Because of the larger relative timing window or cell size within which a transition can be detected, RLL 1,7 is a more forgiving and more reliable code, which is important when media and head technology are being pushed to their limits.

Another little-used RLL variation called RLL 3,9sometimes also called Advanced RLL (ARLL)allows an even higher density ratio than RLL 2,7. Unfortunately, reliability suffered too greatly under the RLL 3,9 scheme; the method was used by only a few now-obsolete controllers and has all but disappeared.

Understanding how RLL codes work is difficult without looking at an example. Within a given RLL variation, such as RLL 2,7 or 1,7, you can construct many flux transition encoding tables to demonstrate how particular groups of bits are encoded into flux transitions.
In the conversion table, specific groups of data that are 2, 3, and 4 bits long are translated into strings of flux transitions 4, 6, and 8 transition cells long, respectively. The selected transitions for a particular bit sequence are designed to ensure that flux transitions do not occur too closely together or too far apart.

Table 8.3. RLL 2,7 Data-to-Flux Transition Encoding

Limiting how close two flux transitions can be is necessary because of the fixed resolution capabilities of the head and storage medium. Limiting how far apart two flux transitions can be ensures that the clocks in the devices remain in sync.

You might think that encoding a byte value such as 00000001b would be impossible because no combinations of data bit groups fit this byte. Encoding this type of byte is not a problem, however, because the controller does not transmit individual bytes; instead, the controller sends whole sectors, making encoding such a byte possible by including some of the bits in the following byte. The only real problem occurs in the last byte of a sector if additional bits are necessary to complete the final group sequence. In these cases, the endec in the controller adds excess bits to the end of the last byte. These excess bits are then truncated during any reads so the controller always decodes the last byte correctly

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Why flash drive is prone to much more damages?

Flash DrivesFlash drives have just changed the lives of students, teachers, businessmen, engineers and other working people for their IT jobs. A flash drive comes up with a lot of features including its light weight, small size, portability, reliability, trustworthiness and large storage ability comparable to the existing removable devices. This is a great external storage device – now you can save even a movie or bulk of files in it which was not possible before in punch cards or later in floppy diskette due to their insufficient space of storage.

There are a number of factors which cause for its failure and they don’t allow flash to read and write any data file.

Flash drive is small in size so there are many chances of being misplaced and smashed up going under any heavy gadget.
Flash drives are an easy source of spreading viruses from one PC to the other.
Flash drive can easily be stolen due to its small size.
Extreme temperature may become the cause for destroying its internal circuitry.
Water droplets can also damage flash drive’s functionality.
Data residing in the flash drive can be lost due to its inappropriate removal from computer.
If a flash drive is attached with computer and power fails at the same time then there might be a chance of data loss residing in the flash drive.
Flash contains so many benefits along with number of drawbacks but still it is useful. It is adopted by large number of users.

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Undelete Freewares

Undelete Freewares1. Freeware: Undelete Plus

  • License: Freeware (limited time)
  • OS: Win 95/98/Me/NT/2000/XP/2003/Vista
  • Publisher: Phoenix Technologies LTD.
  • File System support: supports all Windows file systems for hard and floppy drives including FAT12/16/32,NTFS/NTFS5 and image recovery from Compact Flash, Smart Media, Multi Media and Secure Digital cards.
  • Screenshot: http://www.undelete-plus.com/screens.html
  • Description: A quick and effective way to restore accidentally deleted files. It can also recover files that have been emptied from the Recycle Bin, permanently deleted files within Windows using the Shift + Delete, and files that have been deleted from within a Command Prompt.

2. Freeware: Undelete NOW!

  • License: Freeware (email required)
  • OS: Win 95/98/Me/NT/2000/XP/2003/Vista
  • Publisher: WCCL
  • File System support: Every kind of disk, including FAT 12/16/32 and NTFS (including compressed and encrypted) partitions. It supports regular hard disks, backup disks, USB drives, and any other disks shown in Windows Explorer.
  • Screenshot: http://www.undelete-now.com/undelete-now/screenshots.aspx
  • Description: Undelete NOW! recovers your lost files, no matter how they were deleted. Using powerful bit-by-bit scanning methods, you can be sure to get your files back quickly and easily.

3. Freeware: NTFS Undelete

  • License: Freeware (open source)
  • OS: 2000/2003/XP/Vista
  • Publisher: A-FF Labs
  • File System support: NTFS
  • Screenshot: http://ntfsundelete.com/img/screenshot.png
  • Description: NTFS Undelete is free and open source software that allows you to recover deleted files. It recovers files directly from hard drive, and it will work even if you empty Recycle Bin.

4. Freeware: EASEUS Deleted File Recovery

  • Version: 2.1.1
  • License: Freeware
  • OS: Windows 2000/2003/XP/VISTA
  • Publisher: CHENGDU YIWO Tech Development Co., Ltd.
  • File System support: Supports FAT 12, FAT 16, FAT 32 and NTFS file system.
  • Screenshot: http://www.easeus-deletedrecovery.com/screenshots.html
  • Description: EASEUS Deleted File Recovery is a fully functional freeware designed to recover deleted files from all types of media such as Hard Disk Drives, Floppy Drives, Smart Media, Compact Flash, Memory Sticks, and other types of removable media.

5. Freeware: Smart Data Recovery Enterprise

  • License: Freeware
  • OS: NT/2000/XP/2003/Vista
  • Publisher: Smart PC ® Solutions, Inc.
  • File System support: Supports FAT 12, FAT 16, FAT 32 and NTFS file system.
  • Screenshot: http://www.smartpctools.com/network_data_recovery/screens/netrecovery2.jpg
  • Description: Recover deleted files and data remotely over the network. Smart Data Recovery Enterprise is a free and easy data recovery solution for network administrators. Undelete files and data remotely without leaving a chair!

6. Freeware: Recover Files

  • Version: 2.1
  • License: Freeware
  • OS: Win 95/98/Me/NT/2000/XP/2003/Vista
  • Publisher: Undelete & Unerase, Inc.
  • File System support: Supports FAT 12, FAT 16, FAT 32 and NTFS file system.
  • Screenshot: http://www.undeleteunerase.com/screenshots.html
  • Description: A professional file recovery software that allows it’s user to recover accidentally deleted files. Even files removed from the Recycle Bin, network drive, compact flash card, portable drives, in a DOS window, or from Windows Explorer with the SHIFT key held down.

7. Freeware: DATA Unerase Personal Edition™

  • License: Freeware
  • OS: ME/NT/2000/XP/2003 and Vista
  • Publisher: OctaneSoft
  • File System support: FAT 12, FAT 16, FAT 32 and NTFS file system.
  • Screenshot: http://www.octanesoft.com/screenshots.php?prog=edata&page=2
  • Description: eDATA Unerase Personal Edition is software used to restore files that have been deleted through normal methods, including accidental deletions from the recycle bin. This is a freeware and basic version of eDATA Unerase. It recovers only deleted files located on local logical disks visible by host OS. This version will not find lost files.

8. Freeware: Recuva – File Recovery

  • Version: 1.24.399
  • License: Freeware
  • OS: Windows Vista, XP, 2003, 2000 and 98.
  • Publisher: Piriform Ltd.
  • File System support: FAT 12, FAT 16, FAT 32 and NTFS file system.
  • Screenshot: http://www.recuva.com/screenshots
  • Description: Recuva (pronounced “recover”) is a freeware Windows utility to restore files that have been accidentally deleted from your computer. This includes files emptied from the Recycle bin as well as images and other files that have been deleted by user error from digital camera memory cards or MP3 players. It will even bring back files that have been deleted by bugs, crashes and viruses!
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CD and DVD utilities

CD DVD UtilityMagic Disk
Virtual CD/DVD driver. With this program you can access or mount an ISO image as a virtual CD/DVD drive just like any regular CD/DVD drive. Supports multiple CD/DVD image formats, including: iso, bin, cif, nrg, etc. Freeware for Windows.

Burn4Free
Free DVD and CD burning program for Windows.

BurnCDCC
This freeware utility can be used to burn an ISO file to a CD/DVD disc. Useful e.g. when you have downloaded a Linux OS installation ISO file from the Web.

IsoBuster
CD and DVD data recovery tool. It supports all CD and DVD formats and all common CD and DVD file-systems. Not free.

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File Formats and File Extensions

Dot What!?
Database of file format extensions, mainly for Windows, but also Apple Macintosh and Linux.

File formats and their Extensions
Large list with thousands of file formats.

File-Extensions.org
A search engine and large list of file extensions. Each file extension comes with an explanation on the way it is used today.

FileExt
Search engine for file extensions. It will find the type of file a file-extension represents and/or the program using that file type.

The Graphics file formats page
Graphics file formats, programming code, FAQs, etc.

Webopedia
Data formats and their file extensions.

Wotsit
Information on hundreds of different file types and all sorts of other useful programming information; algorithms, source code, specifications, etc.

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