CET1171 Lecture #12 - Magnetic Storage

Materials:
Working complete PC
Blank Diskette
Student Diskette, "New Boot A Ver 2.0+"
Objectives:
Understand the basic principles of magnetic storage,
Understand how to install and configure conventional floppy drives,
Understand how to configure IDE hard drive ID's,
Be able to properly attach the drive to the controller,
Be able to configure the drive in BIOS,
Understand hard disk partitions.
Competency:
The student will learn the basic concepts of magetic storage disks, permanent and removable media and their controllers. The student will perform the procedure of installing a new empty HDD. The student will learn the concepts of the IDE bus including device ID's, BIOS configuration and controllers. The students will get hands on experience in handling the task of setting jumpers on the drive correctly as well as physically attaching the HDD to the system. The student will learn the concepts of hard disk drive storage on the PC including partitions. The student will learn how to use the tools to allocate these storage spaces on the HDD.

Floppy Diskette Drives

  1. The floppy disk was the first magnetic mass storage device used by the IBM PC and has been an integral part of the PC architecture since its debut in 1981. Only in the last few years has it begun to disappear from standard PC installations. Despite the fact that the standard floppy drive and controller are now considered deprecated technology (still supported but will no longer be manufactured or supported in the future) it is the simplest of storage technologies and is also the most universal in that all but the latest systems either have a floppy disk drive that they can boot up from, or can have one installed temporarily to work from (although there are new motherboards that no longer feature floppy disk controllers they usually have a BIOS that will accept an external USB floppy drive as if it were a standard one).

  2. The FDD - Floppy Disk Drive itself is responsible for the actual work of formatting a diskette (marking out tracks and dividing them into sectors) and locating tracks and sectors and reading/writing information to and from these sectors. The peripheral that makes these requests is the FDC - Floppy Disk Controller. This is the device that attaches directly to the expansion bus and all access requests actually go to this device and it then forwards requests to the drive(s) along the data ribbon cable.

  3. The physical and logical layout of the floppy diskette is that it is a single disk of magnetic storage film similar to a flat disk of cassette tape material. However, it should be noted that the floppy disk material is far superior in recording quality.

  4. The diskette has a door that the drive internal mechanics will clamp and pull aside exposing the surface of the disk through the window in this door. The read/write/erase heads can then be moved into position to operate on this exposed storage surface. These heads make physical contact with the diskette and will eventually wear the surface out, making the diskette the least reliable of all storage devices on the system.

  5. This wear also occurs on the heads and eventually they will wear out and fail as well. Also consider that the drive's internal mechanics are directly exposed to the environment through the front opening so the drive does accumulate dust as well as diskette surface residue over time which will lead to its eventual failure as well. There are floppy drive head cleaning kits but their quality and effectiveness is dubious at best. Once a drive appears to be failing on diskettes that are perfectly fine in another drive, they are cheap enough and easy enough to replace that this is the best action to take in such a case.

  6. The drive stores information on the bottom surface as well as the top surface with independent read/write/erase heads but these are suspended from the same arm assembly and so sweep across the tracks together.

  7. The original standard floppy disk controllers supported a maximum data transfer rate across the cable from the drive to the controller (or vice versa) of 250Kb/sec which was respectable in 1981 but rather exasperatingly slow in modern times.

  8. The first standard floppy disk drive attached to this controller was a 5 ¼" 360KB floppy drive. These are certainly rare in daily usage any more.

  9. The "minidiskette" or 3 ½" floppy drive was spearheaded by Sony and because of the fact that the disk is protected within a stiff (non-floppy) plastic shell rather than a truly floppy paper shell of the earlier diskettes it became very popular and very quickly became the standard floppy disk and drive for the IBM AT. The first 3 ½" drives and diskettes had a 720KB storage capacity and still worked with the original 250Kb/sec floppy disk controller. This device had evolved over time from being on an ISA expansion card to being built directly into the motherboard.

  10. This was convenient since it reduced the slot count and therefore the manufacturing cost of the motherboard, but if it failed this would cause quite a bit of trouble. Better BIOS designs allow the built in controller to be turned off so that an expansion card controller can be installed if the built in one fails so it will not conflict with the integrated one. This situation and the lessons learned from it would apply to all integrated motherboard peripherals of the future including Pentium based systems that have all necessary peripherals built into the motherboard and need no expansion cards at all in order to work.

  11. The development of a 3 ½" 1.44MB diskette which has double the number of sectors per track, but still spins at the same RPM (Rotations Per Minute) caused some trouble. Because it has double the sectors per track but spins at the same RPM, this means that the data stream is crossing the heads twice as fast and in fact a new floppy disk controller had to be developed that would support the 500Kb/sec speed of this drive. As this controller standardized rapidly including expansion card versions to support the new 1.44MB capacity diskette and drives, it quickly became the standard.

  12. IBM developed a 2.88MB 3 ½" diskette for their PS/2 line of personal computers. The technology never caught on as users realized that in order to use a 2.88MB floppy diskette, they needed a drive that could format and read this capacity, and worse: they would need to upgrade the floppy drive controller to one that could support 1Mb/sec transfer rates and users did not want to replace the controller as well. The capacity of the 2.88MB diskette is due to double the number of sectors/track spinning at the same RPM so the data passing the heads is double that of the 1.44MB 3 ½" diskette and drives.

  13. The head assembly is on a swinging arm that is positioned by a stepper motor. The electric motor that most people are familiar with is one that spins, but a stepper motor moves a partial rotation when power is applied rather than complete constant rotations.

  14. The hub of the diskette has two holes that allow the hub clamp to grab it. In modern floppy drives the electric motor that spins the hub clamp is directly attached to it on a single shaft and the drive uses an RPM sensor to adjust the RPM and keep it constant so that data will pass under the heads at the proper speed so that it will be read (and written) and delivered to the system correctly. In older drives the hub clamp was attached to the motor, which was located at the back of the drive, with a belt. Slippage in the belt as it aged caused many floppy diskette read/write errors which encouraged the introduction of the direct drive with automatic RPM adjustment capability making the 3 ½" 1.44MB floppy disk drive far more reliable, not because of anything other than this design decision.

  15. The four generations of floppy diskette drive attach and work with two generations of floppy disk controller. The newer controllers are backwards compatible and will accept the two older types of floppy diskette drives.

    Name Capacity Tracks Sec/Trk Transfer Rate RPM
    5 ¼" DD (Double Density) 360KB 40 9 250Kb/sec 300
    5 ¼" HD (High Density) 1.2MB 80 15 500Kb/sec 360
    3 ½" DD (Double Density) 720KB 80 9 250Kb/sec 300
    3 ½" HD (High Density) 1.44MB 80 18 500Kb/sec 300
    3 ½" ED (Extra Density) 2.88MB 80 36 1Mb/sec 300

    (2.88MB Extra Density drive is included for completeness but was never truly a standard. Xfer Rate means Transfer Rate.)

  16. The floppy disk drive along with all technologies in the PC has evolved in several aspects not the least of which is performance and capacity; the two technological advances that most users notice. But what people seldom pay much attention to are the other equally significant technological advances: miniaturization, reliability, and compatibility. The floppy disk drive has certainly become smaller.

  17. A system that originally came with either a 5 ¼" 360KB floppy drive or a 3 ½" 720KB floppy drive will more than likely have the 250Kb/sec floppy drive controller and will not be able to use the higher capacity drive at that capacity. Note that the higher capacity diskettes are often capable of being formatted at the lower capacity, so a 3 ½" 1.44MB floppy diskette can function as a 720KB diskette but the diskette's media sense holes will have to be blocked so that the drive will think that the diskettes are 720KB diskettes and not 1.44MB diskettes.

  18. The diagram above illustrates a top view of the diskette, the direct drive hub motor is located below the diskette and the read/write/erase head assembly can be seen attached to the end of the swing arm attached to the stepper motor that positions it. This arm is shown stepped at three different positions. The red ring is the surface of the diskette that is passing under the head assembly in its current position as the diskette spins underneath it. The head assembly of the drive can either erase (destroy), read, write or format (create) sectors anywhere on this track while it is in this position.

  19. While a drive could be developed that could read or write a single byte of data to anywhere on the surface of the diskette, it was found that this would be far too inefficient and time consuming for the electronics and mechanics of the disk to find the exact location of the desired byte. Instead the tracks are divided into sectors. Remembering that the disk is a magnetic storage device then information is written to and read from its surface in the form of small magnetized regions along the tracks. If the region(s) North-South orientation is a certain way, then it is a "one" if it is another way then it represents a "zero." (Note: this is not really true, but it is close enough to understand what the drive is doing, the truth is far too deep and ugly to deal with here.)

    Items Indicated
    1. Media Sense: If there is a hole in the upper left hand corner (while looking down at the top of the diskette with the surface door at the bottom), then it is a 1.44MB capacity 3 ½" floppy diskette. If the hole is missing then the drive will attempt to access it like a 720KB capacity 3 ½" floppy diskette.
    2. Write Protect: If this tab is closed (no hole) then the drive will enable the write/erase heads and allow the diskette to be written to as well as read from. If the tab is open (there is a hole) then the drive will disable the write/erase heads and the diskette can only be read from but not written to. Within the drive there is a small optical sensor positioned here and if the light can shine through the hole and reach the sensor then it will disable the write/erase heads. It would therefore be possible for the light source to fail and then a write protected floppy would be written to, but the author has never heard of this happening.
    3. The hub clamp area.
    4. The opening in the exterior shell of the diskette that exposes the surface area so that the head assemblies can access it.
    5. The surface exposure door pulled back so that the surface of the diskette is exposed to view.
    6. The data tracks along the surface of the diskette (figurative of course they are magnetic and therefore not visible to the human eye)
    7. A sector along the track.

  20. So along the tracks there are regions that lie between the actual sectors of data that are written the by the drive heads that say: "This is the end of the preceding sector" or the end-of-sector marker. This would be followed by "The following sector is sector #5" (for example) or the sector number. This would be followed by "The check sum of the data in the following sector is CDE0F166h" (for example) or the sector data checksum known as the CRC - Cyclical Redundancy Check. This would be followed by "After this series of codes the data of the sector begins" or the start-of-sector marker. These intersector gaps will be described in detail in the HDD - Hard Disk Drive section below.

  21. So as the diskette spins under the heads and they begin to read the values, the heads will cross the End-of-Sector marker and recognize this and read the sector number of the next sector, the checksum of its data, and the Start-of-Sector marker for the upcoming sector and then read the data. If it was sector #5 and the read request was for say sector #10 on this track, then the drive knows to just watch these sector boundaries until it reaches sector #10, then collect the checksum and then read the data up.

  22. A sector holds 512 bytes of data within in it, but the preceding intersector gap can be large enough that when added to the actual data it holds that it is closer to 600 bytes. This is why the diskette is sometimes referred to as having a 1.44MB "formatted" capacity meaning the total of the data storage capacity of the sectors not including the intersector gap data which can never be used by the user.

  23. The student has already used the FORMAT command to format a floppy diskette and to also place the DOS kernel files on it making it a bootable diskette (format a: /s) It is this FORMAT command that positions the heads over track zero and then requests to the drive to generate fresh new intersector gap information effectively destroying all existing sectors and creating new ones. Once that track is complete it advances the head assembly to track #1 and creates new sectors around it and so on until the entire diskette has been formatted.

  24. Here is another exterior view of the bottom of the diskette showing the hub clamping area and the media sense hole and write protect tab. Remember that when looking down at the top of the diskette the write protect tab is in the upper right corner and when looking down at the bottom of the diskette it is in the upper left hand corner.

  25. The standard 3 ½" 1.44MB floppy diskette and floppy diskette drive support 18 sectors per track and they are divided like slices of a pie. The diskette and the drive support a total of 80 tracks, meaning that the head assembly stepper motor can step through 80 discrete positions through the open window when it is pulled back exposing the surface to the head assembly.

  26. The read/write/erase head assembly has a separate head that accesses the bottom surface of the diskette and there is a separate read/write/erase head attached to the same swing arm that accesses the top surface of the diskette at the same time. But only one head within the head assembly can actually operate at a given time, the drive switches from one to the other as needed.

  27. So the diskette has 80 tracks divided into 18 sectors each: 80 x 18 = 1440 sectors. But there are this many sectors on the bottom surface (side 0 or head 0) and there are this many sectors on the top surface (side 1 or head 1). So 1440 sectors x 2 = 2880 total sectors.

  28. Since each sector is 512 bytes and 1KB is 1024 bytes and 512/1024 = ½ Then it can be said that each sector is exactly ½ KB in size. 2880 sectors x ½ KB/sector = 1440KB. Now this value was erroneously divided by an even 1000 to yield the conversion to 1.44MB. But 1440KB is entirely accurate as far as formatted data capacity is concerned.

  29. Boot up and enter the BIOS Setup Utility. This section of the BIOS software is only entered when the user specifically calls for it usually by holding the [DELETE] key during boot up. But other machines have different keystrokes for entering their BIOS. Some require: [F1], [F2], [F10], [SHIFT]+[DELETE], [CTRL]+[S], etc. If none of these work then it might be necessary to go on line and find the manufacturer's website to find out what the key combination is.

  30. Depending on the particular BIOS, the location of the setting for the boot sequence will vary from one to another. Find the boot sequence setting, consult the motherboard manual if necessary and set the boot sequence to be sure that it will boot to the floppy drive A: first. The documentation should also explain how to save the changes and exit the BIOS Setup Utility. Upon exiting, the system will reboot.

  31. As mentioned earlier the floppy drive like all other technologies in the PC has improved in areas other than just speed and capacity. Not only are the drives physically much smaller and the lessons learned from the early designs led to the improvement of the spindle motor into an autoRPM compensating direct hub drive design, but the floppy drive has also improved in the area of compatibility despite the fact that it attaches to the floppy disk controller which is a standard ISA device, a bus that does not lend itself to ease of installation nor compatibility. However, the twist in the cable and the BIOS Setup Utility virtually eliminated the need for setting jumpers on the drives making them much easier to install. The main trouble with setting the jumpers on the floppy drive was that the locations of the various jumpers varied from one manufacturer to the next and they rarely bothered to indicate directly next to the jumpers what they meant. The Internet had not been "invented" yet so without documentation the floppy drive was virtually useless.

  32. Open the case and put on the antistatic wrist strap. Remove the power cable and data ribbon cables that are attached to the floppy disk drive. Pay close attention to the orientation of the power cable connector (the white plastic connector with one yellow wire, one red wire and two black wires attached to it that runs back to the power supply). Also pay very close attention to the orientation of the ribbon cable. Even though many are keyed with a small slot in the connector of the drive into which a plastic protrusion on the ribbon cable connector fits and will prevent it from being inserted if it is turned over, the cable has a pin #1 marked on it. Some are solid red and others are a very faint pink stripe. Be sure that you know which side of the floppy drive connector this Pin #1 faces when the cable's connector is inserted.

  33. Remove the screws that are anchoring the floppy drive to the case. Slide the drive forward and out of the PC. With the floppy drive removed, start up the PC and enter the BIOS Setup utility. Consult the motherboard manual if necessary to determine how to disable the onboard floppy disk drive controller, locate this setting and disable it. With this peripheral disabled, no floppy drive will be able to communicate with the system and vice versa. Now locate the setting for floppy drive A: and change it from 3 ½" 1.44MB to "none." Save the changes and exit the BIOS Setup Utility.

  34. As the system reboots turn it off. The system is now physically devoid of floppy drives and the firmware is devoid of them as well. Firmware is another term used for the BIOS. This refers to program logic that is embedded permanently in a physical chip. It is software, but it is also a chip or hardware, hence the term "firmware" indicating that it is software but in a physical package like the BIOS ROM chip is.

  35. Now reattach the floppy drive to the ribbon cable and the power cable and leave it resting face forward on the top of the drive mounting bays. Be sure to connect the ribbon cable correctly. Pin #1 is indicated as a red stripe down one edge. This must connect to the Pin #1 side of the block pin jumper connector on the drive itself. The drive can indicate Pin #1 with a small number near it, a small arrow near it or a missing pin near it. Pin #2 is not used and is sometimes omitted to indicate that Pin #1 is next to it. Attach the power cable to the drive using the way it was found as the guide. Be very careful, the power connector for the floppy drive can be inserted upside down and will cause a short circuit that will destroy the drive and possibly the power supply as well.


    Floppy Disk Drive Data Ribbon Cable Attachment


    Floppy Disk Drive Power Cable Attachment

  36. Will this floppy disk drive be the A: drive or the B: drive? Be sure that the drive is attached to the connector that is beyond the twist in the cable. Follow the cable up from the motherboard. Usually the length from the motherboard connector to the first drive connector is the longest section of the cable: this is the "long run." The first connector encountered is the attachment for the B: drive. Then there is a twist in the cable and the connector beyond it is for the A: drive.

  37. The twist in the standard 34-pin/wire ribbon cable changes some connections to the drive effectively automatically changing the settings for the drive beyond the twist to be floppy drive A: and the drive before the twist will be the B: drive. This makes the standard floppy data ribbon cable "position sensitive" or a drive "cable select" cable. All modern 3 ½" floppy disk drives will respond correctly to this but it should be noted that older floppy drives (usually 3 ½" 720KB or the old 5 ¼" drives of either 360KB or 1.2MB capacities) might not necessarily respond correctly to this cable and may require the jumpers on the drive to be set in order to set the capacity, data transfer rate and whether the drive should be the A: drive or the B: drive. These drives are very old and the jumper settings are usually proprietary, finding the information on how to set them could be quite a challenge.

  38. Be careful when attaching and detaching the data ribbon cable (and of course the power cable and any other connector in the PC). Block pin jumper connectors also known as IDC - Insulation Displacement Connector such as those used on the 3 ½" floppy drive connector and data cable push straight in and pull straight off firmly but should not need to be forced too much. Be sure that the female connector of the cable is exactly lined up with the drive's male connector pins and that it is not backward before pushing it into place. Be sure that the connector is pushed all the way on snuggly and securely. Loosely attached data cables lead to bizarre errors and future failures as they gradually loosen with heating and cooling and vibration of the drive itself.

  39. There is a strange error that crops up from time to time with floppy drives that is often associated with a loose data cable called the "phantom drive." This occurs when a floppy diskette is accessed, then removed and another one is inserted and it appears to have exactly the same information on it as the previous one. If the second one is not a clone of the first one then beware, DOS is about to damage it and here is why.

  40. Later versions of DOS including of course version 6.22 and the Windows 9x versions all prefetch the floppy diskette's layout information stored in its boot sector as well as the root directory information and keep this information cached in RAM to improve floppy disk access performance. The FDD (Floppy Disk Drive) is able to detect when a floppy disk is removed and sends a signal back to the FDC (Floppy Disk Controller) alerting it that this occurred. The signal travels on pin #34 (the disk "changeline" signal), the outside line opposite to pin #1 on the cable. If a cable is attached loosely this can be the one and only pin that vibrates until contact is lost. If this signal does not make it back to the FDC then the system does not know that the other diskette was removed and continues therefore to use the cached directory and disk layout information of the previous diskette. Writing to the second diskette can cause major directory information damage to it at this point.

  41. To survive with a system that has a bad line #34, be sure that the current drive is the C: drive (or any drive other than the floppy A: drive) and when a diskette is removed attempt to read it (DIR A:) before inserting the next diskette. DOS will report a failure and an "Abort, Retry, Fail?" prompt. Tell it to abort (type [A]) and then attempt to read it a second time and abort the error a second time (twice just to be sure that DOS acknowledges that the cached information is no longer valid since it can't read the diskette) and then insert the new one. Upon reading it the contents should be correct.

Hard Disk Drives

  1. The HDD - Hard Disk Drive is the primary mass storage device of the PC. The actual IBM PC introduced in 1981 was not equipped with a hard drive, but instead boots up from a 5 ¼" 360KB floppy diskette which had the entire operating system on it and any programs and data files created would have to be on another diskette which the user inserted after removing the boot floppy.

  2. Seagate was one of the first companies to manufacture a PC compatible hard drive controller as an expansion card for the ISA bus and the hard drive attached to this controller by two ribbon cables: the data ribbon cable and the control ribbon cable that carried the signals to the onboard mechanisms and motors of the drive. This technology started as the Seagate ST-506 hard drive and controller but it was the ST-412 hard drive and controller that first appeared as a third party upgrade for the IBM PC. These are often called ST-506 drives even though they are really ST-412's. ST-412's are full height 5 ¼" hard drives (the size of a CD-ROM drive but more than twice as tall) with a formatted capacity of 10MB. Laughable now, but they were immense compared to the 360KB floppies that everyone had to use otherwise. IBM would include them as standard equipment on the second personal computer model introduced in 1982: the IBM XT.

  3. The ST-412 technology introduced a low level BIOS interface on the expansion cards of the hard drive that would ultimately reach integration into the motherboard BIOS with the IBM XT and support within the MS-DOS kernel allowing it native support of hard drives. Once this happened, the low level access functions could not be changed without instantly rendering obsolete uncountable numbers of computer systems, programs, and users. The choices made in the early days, and not all of them were good ones, would be inherited down through time all the way to the Pentium era before things would take a much needed leap forward and escape the inherited shortcomings of these ancestral drives and their low level BIOS code.

  4. The main problem with the ST-412 was the overwhelming urge to remove the drive from one PC with an ST-412 controller card and attach it to another PC with an ST-412 controller card. And this was absolutely doomed to failure because the controller was made for that particular drive. It was programmed with the factory defect map of which sectors it could use and which ones simply could not store information. Most users did not know the convoluted process of reprogramming the defect map and the system had no way of automatically detecting manufactured surface flaws. If the user decided to "fix" the problem with a low level format operation, which unfortunately depends on this very defect map in order to avoid the problem areas on the surface of the drive, matters would just get worse.

  5. Attempts were made to create a technology in which drives could be swapped out that the controller could work with, but the defect maps are peculiar to the hard drive and it was evident that until the low level controller circuitry was embedded onto the hard drive itself, this problem would persist.

  6. With custom circuitry manufacturing, the industry had an opportunity to begin the miniaturization of the controller card and attempts were made to develop a universal interface to the ISA bus, but each manufacturer would modify any shared ideas and ultimately end up with a custom controller based on the shared standard that deviated enough that only their own hard drives would work properly with it. One such technology was ESDI – Enhanced Small Device Interface.

  7. The industry leaders finally got together and forged a new standard that would be fully universal and compatible and most importantly, the companies adhered to the standard so that in the end it worked extremely well and now all hard drives will work with any hard drive controller. This hard drive technology is called IDE – Integrated Drive Electronics even though it is actually part of the standard for the controllers which are called ATA - Advanced Technology Attachment controllers and specifications.

  8. The hard card above demonstrates an evolutionary half way point toward true IDE. The main accomplishment of IDE is that the hard drive's controller is mounted directly onto the hard drive itself thus eliminating the problem posed by the ST-412 technology of the two being separable by the user. In this hard card, the controller is a full size ISA card and the 50MB HDD is mounted directly on the card, so the two move from one PC to another together as a single unit. The difference is that the HDD cannot be replaced on the hard card.

  9. The manufacturers found that they would only actually ever use 40 wires within the standard ISA bus. There were many IRQ lines, and DMA channel signal lines and so forth in that bus that they would never attempt to use. So instead of attaching the drive directly to an ISA slot with an ungainly card edge connector on the end of the data ribbon cable, they instead brought the 40 wires of the ISA bus that they had chosen to use out to a standard two row male block pin header to which a standard 40 wire ribbon cable with a standard IDC40 could be easily attached. All of these items already existed in the electronics industry which is why this was done. This technology was referred to as "XT IDE" even though it is based on the IBM AT's 16-bit ISA bus.

  10. But directly attaching the IDE drive to the ISA bus caused problems on occasion especially if the drive was experiencing trouble, it could crash the ISA bus and effectively paralyze the entire PC and even prevent it from rebooting. A set of circuits had to be introduced to separate the hard drive from the ISA bus so that this would never happen.

  11. Once the manufacturers saw that they were going to be forced to introduce circuitry between the IDE drive and the ISA bus, they decided to create a universal controller and rework the language and the signals that traveled down the 40-wire ribbon cable in order to make the signaling and the language more "hard drive oriented" than the standard universal expansion bus signals of the raw ISA bus. This universal interface controller for IDE hard drives is called the ATA controller which interfaced at first to the ISA bus and later to the PCI bus. ATA controllers have evolved through 7 generations since their debut with the first true IDE hard drives and are only now (in 2005) seeing their last days as the standard general purpose storage technology that held the operating system, programs, and user data on hundreds of millions of PC's for over a decade.

  12. Hard drives themselves all function similarly from the ST-506 through the modern high capacity SATA – Serial ATA (the current standard hard drive technology) and SCSI – Small Computer System Interface drives. Hard drives are high capacity magnetic storage devices that store information as small magnetized regions on the surface of circular tracks arranged in concentric rings across one or more rigid metal platters; hence the term "hard drive" distinguishing it from the "floppy" drive in which the storage disk is a non-rigid sheet of plastic impregnated with iron oxide (rust, by the way.)

  13. The hard drive has a head assembly similar to the floppy drive but with multiple heads fixed to it one for the top of the first platter, one for the under side of the first platter, one for the top of the second platter and so on. This HDA - Head Disk Assembly sweeps all of the heads from side to side together and is moved by a single stepper motor just like the floppy drive.

  14. The heads of the hard drive never make physical contact with the platters while they are actually in use reading, writing, erasing and formatting data to the disk surfaces and only touch the platters in specific areas designed for this called landing zones.

  15. Hard drives spin at thousands of RPM and the heads are mounted into a unit designed to ride on the cushion of air blowing off of the spinning platters beneath them. If they do come in contact with the storage surface they are likely to damage the thin magnetizable surface film of the platter and also warp the head unit designed to ride on the air cushion thereby permanently damaging the head so that it will no longer ride on this cushion of air correctly any more either. This event is referred to as a head crash and this is quite likely to result in catastrophic data loss and possibly a complete and permanent failure of the hard drive.

  16. So it can be seen that the head assembly is one structure that is turned slightly with each step of the stepper motor and that action will position all of the heads over their next tracks. This entire structure is sealed within the drive housing which has a microscopic particle filter to prevent any foreign objects from getting inside. This is critical because the heads ride only millionths of an inch above the surface of the platters. This is so close that a particle of smoke cannot fit between the head and the platter and can in fact cause a head crash. Needless to say, once a modern drive is opened, it is easily ruined because of particulate contamination and, in fact, the manufacturers build the drives, recondition them, and open them to remove the platters to attempt physical data recovery in "clean rooms" that are completely particle-free controlled environments that have air conditioning systems whose microscopic particle filters alone cost thousands of dollars.


    Hard drive dissected showing the finely polished surfaces of the
    platters and the head disk assembly and "voice coil" stepper motor

  17. In hard drives the onboard circuitry activates one head at a time even though they are all riding over the same track number on their respective platters at the same time. So if head 0 is riding over track #0, then head 1 is also riding over its track 0, and so on. All of the track 0's together form cylinder #0.

  18. So the imaginary cylinder is formed by the vertical stack of tracks through all of the platters. Heads number from 0 to the highest number and cylinders also start with cylinder #0 up to the highest number on that drive, but sectors start with sector #1; there is no sector #0 on the tracks in this particular method of locating a sector of information on the surface of the drive.

  19. These intersector gaps between the sectors hold the end-of-sector marker, the upcoming sector number, the sector data checksum or CRC, and the start-of-sector marker so that the drive can locate the data within the sectors along the track. Different manufacturers define different intersector gap codes for these pieces of information in modern drives so the system itself no longer writes these gaps directly as is done during the format of a floppy diskette. These gaps come already written on the drive at the factory and are referred to as the low level format of the drive. The operating system during the format of a modern drive only asks the drive itself to verify the sectors along the track and if a sector fails this verification it will be marked as "bad" within the file system structures so that it will be avoided.

  20. One of the main ways that modern drives have steadily improved is in the area of the stepper motor design. The distance between the tracks has been greatly reduced allowing for many times more cylinders than in older drives. The distance between the tracks is referred to as track pitch and the track pitch of modern drives is as small as 1/100,000th of an inch or smaller. This means that stepper motors can step by these microscopic distances with great precision, being able to step through many thousands of such fine increments and then they can step back over them again and again millions of times during the operational lifespan of a hard drive.

  21. The stepper motors are not perfect however, so an entire platter has been permanently etched with tracks that a special head can follow and tell if it is inline with the desired track and whether it is to the left or the right of it. This head will send this information back to the HDA controller circuitry which will then make very fine adjustments in the position of the head assembly based on the feedback from this special dedicated head reading this special dedicated surface of one of the platters. This is called the servo platter and servo head. Without them, the hard drive could not possibly align itself to the tracks that are simply too fine on modern drives.

  22. Furthermore, as the hard drive heats up after it is turned on, the expansion of the platters from the heat being only a microscopic fraction of an inch is still enough to misalign the heads from the tracks, so the HDD would fail at different temperatures if this servo head were not making these corrections on the fly. Modern drives automatically calibrate periodically based on internal temperature changes. This is why an HDD will briefly chatter from time to time even though the PC is sitting idle, it is the periodic automatic calibration being performed by the servo head, stepping the head assembly across the drive to locate the tracks again.

  23. The total data storage capacity of the hard drive would be the total number of sectors times 512 bytes/sector. If there are a certain number of sectors per track and a certain number of heads, then multiplying the number of sectors/track times the number of heads will yield the number of sectors in the cylinder. For example, a floppy disk has two heads, the top and the bottom of the single platter. If each track holds 18 sectors, then the cylinder made up of the track under head 0 and the track under head 1 would hold a total of 36 sectors or: 18 sectors/track X 2 total heads = 36 sectors/cylinder. Now if the total number of cylinders is multiplied by this number (the total sectors/cylinder) then the result would be the total number of sectors on the drive. Since the floppy has 80 tracks (or cylinders) then 36 sectors/cylinder X 80 cylinders = 2880 total sectors on the floppy disk. Multiplying the total number of sectors on the disk by the total bytes/sector will yield the total storage capacity of the disk so: 2880 sectors X 512 bytes/sector = 1,474,560 bytes which is the exact storage capacity of a 1.44MB 3 ½" floppy diskette. The full formula for finding the capacity of any HDD would be given by:

    HDD Capacity:
    C x H x S x 512 = Capacity in bytes
    Where:
    C = Total cylinders
    H = Total heads
    S = Total Sectors/Track 
    

  24. The total number of cylinders, heads, and sector/track of the HDD is called the drive's geometry. In older drives the geometry was not printed on them nor was the information concerning the jumper settings needed to properly configure the drive to function. On modern drives this information is usually printed on a sticker directly on the drive. The geometry of the drive is sometimes referred to as CHS - Cylinder Head Sector.

  25. For example, a particular HDD has the following values printed on its factory sticker: C=929, H=8, S=55. The storage capacity of this drive would then be:

     929 x 8 x 55 x 512 = 209,735,680 bytes
    

    If this is divided by a binary megabyte (1,048,576) the result is: 200.01953125 or rounded simply to 200MB. However, hard drive manufacturers never use the binary megabyte equal to 1,048,576 bytes, and instead they divide this total true capacity by even millions. This means that the drive manufacturers would print on the box of this hard drive: "210MB IDE HDD" The fine print on the side of the box says something to the effect of "MB as we define it to mean exactly 1,000,000 bytes"

  26. FDISK, FORMAT and all of the other tools that actually work with the physical device cannot redefine the megabyte to their particular tastes or they will not be setting up partitions or formatting the real drive that works in the real world with real binary number systems and capacities. This means that FDISK and FORMAT will report the "210MB" drive's capacity correctly as 200.02MB. This discrepancy has throughout time caused as many end user concerns as real problems with the hard drive. The situation continues in modern drives in which the "40GB" capacity printed on the box is using "GB as we define it to mean exactly 1,000,000,000 bytes" and it is not therefore 40GB of GB's equal to 1,073,741,824 bytes.

  27. It is entirely accurate to multiply the C x H x S part of the formula then divide this number by 2 and place KB after the result. This is because 512 bytes is exactly ½ KB. So the formula can also be written as C x H x S x ½KB = Capacity in KB. On the example above the drive would then be given by: 931 x 8 x 55 = 409640 (sectors) ÷ 2 = 204,820 KB. This number is totally accurate. Divide it by 1024 to get totally accurate capacity in MB (binary MB and not even 1,000,000 byte MB): 204,820 ÷ 1024 = 200.01953125 which is the exact result from before.

  28. Geometry is used by the BIOS to find a particular sector on the hard drive to either read the data and deliver it back to the requesting program or to write data to it for the requesting program. A program could request the sector located at Cylinder = 337, Head = 5, sector = 19. There is only one sector on the entire drive that will have those particular geometric coordinates and programs make these kinds of requests to the low level 16-bit BIOS HDD drivers.

  29. The MBR - Master Boot Record already discussed throughout these lectures is the first physical sector of the drive and it is the sector located at Cylinder = 0, Head = 0, Sector = 1 (remember that sectors do NOT start with number zero along the track, they start with sector #1).

  30. With the ATA-2 specification in which a secondary controller was defined, drives were becoming so large in terms of their geometry values that the old BIOS CMOS settings numbers could no longer hold the numbers and BIOS'es were modified to be able to translate numbers so that the old code could still work with the larger drives. Several other improvements were made to the ATA-2 specification including augmenting the IDE language that the controller uses to communicate with the hard drives attached to the data ribbon cable. Manufacturers responded by making superior hard drives that could take advantage of the improvements made to the ATA-2 controllers.

  31. At the same time the hard drive manufacturers discovered that there were specific common values for existing drives that would work very well with the translation calculations or algorithms that the BIOS code was using. So they defined the drives to always report any number of cylinders, but always with 16 heads and 63 sectors/track. Another influence for making this choice was that the HDD technology had just recently transitioned to using ZBR – Zone Bit Recording.

  32. Notice that the outer track of the old geometry drive has eight sectors and the innermost track also has eight sectors. But the outer track is physically longer, on a 3 ½" HDD it is about 11 inches in length (Circumference = Diameter X л) and the inner track where the diameter of it is perhaps 1.1" inches would be: 1.1 X 3.1415… = 3.45… inches. Since each sector holds 512 bytes of data multiply this times 8 sectors = 4096 bytes of data. These 4096 bytes of data fit in 3.45 inches on the inner track and if this same density is maintained on the outer track, then the outer track, 11 inches long should be able to hold 11 ÷ 3.45 = 3.18 over three times as much data.

  33. This greatly improves the total storage capacity of the drive without changing any manufacturing technology, just reprogramming the controller to read and write at a uniform density across all tracks, but this means that each track will have a different number of sectors along it, which means that the old geometric coordinate system cannot work. For example, Track 0 would have a Sector #189. but track 1 would only go up to Sector #186, and Track 3 would only go up to Sector #181, etc. It would be impossible for the BIOS to store all of this information about the number of sectors for each individual track amid thousands of them.

  34. So the drive reports a conventional geometry and when it receives read/write requests to a conventional geometric coordinate, it uses an internal lookup table to find where that sector actually resides physically on the platters and then retrieves it for the system. Since drives were already translating internally and only emulating geometry to the rest of the PC, it was a logical step to assign a specific geometry to report to the BIOS since it is a fiction that gets internally translated anyway.

  35. Western Digital marketed the 2nd generation hard drives under the marketing term EIDE - Enhanced Integrated Drive Electronics which has now become an industry standard term that refers to any hard drive adhering to the ATA-2 specification or beyond. Almost all hard drives that the student will encounter will be EIDE drives. Since all modern EIDE drives since the ATA-2 specification, should report having 16 heads and 63 sectors/track, then this part of the capacity equation is always the same: (total Heads) 16 X (total Sectors/Track) 63 = 1008. Bearing in mind that this is almost an even thousand, then if a drive has 4000 cylinders then: 4000 X 1000 = 4,000,000 sectors. Since each sector is exactly ½ KB then 4,000,000 ÷ 2 = 2,000,000KB or roughly 2,000MB or roughly 2GB. This means that to make a fast rough estimate of the size of a modern HDD just divide the total number of cylinders by 2 and the result is the capacity in MB. Divide that by 1000 and the result is the capacity in GB. Not exact, this is just to establish a rough idea of the capacity of the drive since in the Pentium era hard drives have grown from a few GB to a few hundred GB and an older system might have been upgraded at some point. So one might expect to find a 2-4GB HDD on an old Pentium 90, but discover that it is a 20GB HDD which is quite respectable and worth removing before giving the system away to some worthy cause.

  36. Earlier it was noted that the old ISA bus signals are no longer forwarded through the 40-wire cable. Instead this attaches to the ATA controller and it is that device that interfaces with the expansion bus of the PC. The original specification described the technology down to the engineering level describing voltage ranges and their interpretation as ones and zeros and so forth. The significant definitions for the technician to know are that the ATA controller can only address up to a maximum of two devices. At the signal level they are drive #0 and drive #1 but these terms are never used. The drives are referred to as the "Master" and the "Slave." The reason for this, is that in the original specification, the onboard IDE hard disk drive controller built into the "Master" HDD would also run the internal workings of the "Slave" drive as well. This means that the circuit board on the "Master" would run the spindle and head assembly stepper motors and interpret the data crossing the selected head just like it does for its own internal workings but for the "Slave" drive as well.

  37. This worked fine on two identical drives, and could work fine between different models of HDD from the same manufacturer, but it was doomed to fail when the Master had to control a Slave from a different manufacturer. This is one of the details of the technology that was withdrawn in the ATA-2 specification. Internally the "Master" and "Slave" are only Drive ID's and each operates entirely from its own internal controller from then until the latest versions of the technology.

  38. HDD's cannot automatically assign themselves device ID numbers. This is for the user to do. On hard drives this is done by setting jumpers on the drive. As described in other lectures, jumpers are small pieces of metal with a plastic coating that are inserted over to block pins thereby closing a circuit. So a jumper is a very inexpensive and very small switch. When you apply a jumper over two indicated pins, you are simply closing or flipping a little switch. Hard drives must have their jumper settings checked and possibly set as desired prior to connecting them to the controller because the device ID selection is not and can never be automated nor can anyone assume that the factory setting is necessarily the correct setting for the situation that the hard drive is being introduced to: it is a completely user definable parameter for the HDD.

  39. In modern drives faster than "ATA33" meaning that they have a maximum data transfer rate of over 33MB/sec, the drive must be attached to the controller with an 80-wire/40-pin data ribbon cable also called a UDMA cable since it supports the higher speed UDMA modes developed in the latest ATA/IDE specifications. This cable is position sensitive meaning that like the floppy disk drive, the position of the drive on the cable will determine if the drive is the Master or the Slave. However, in order for this to work properly, the HDD must still have its jumpers set to a position that allows it to get its device ID from the cable position. This third possible device ID jumper setting is often referred to as "CSEL" for Cable Select. On UDMA cables the connectors are color coded: the blue connector must be attached to the ATA controller usually on the motherboard, the intended Master drive must be attached to the black connector and the intended slave drive must be attached to the gray connector.

  40. With the ATA-2 specification, a second "controller" was added to the standard. This meant that a system could now have two independent data ribbon cables attached to two independent 40-pin headers on the motherboard or an expansion card ATA-2 or more often called an EIDE controller. These are called the Primary controller and the Secondary controller, but they are in fact run by the same controller circuitry in most cases and would more appropriately be called the Primary and Secondary Channels, but they are only sometimes referred to like this.

  41. An original ATA or IDE equipped motherboard would then feature a single 40-pin male pin jumper set to accommodate a single 40-wire data ribbon IDE cable and it would therefore support a maximum of two IDE devices. An ATA-2 or EIDE equipped motherboard (or expansion card) would feature two 40-pin male block pin jumper sets or IDC (Insulation Displacement Connector) connectors to accommodate two 40-wire standard IDE data ribbon cables or 80-wire/40-pin UDMA cables and could therefore support up to 4 devices.

  42. From the original ATA/IDE technology optical drives were adapted to be attached to the ATA controller, but they are not hard drives and are many orders of magnitude (means: tens, hundreds, thousands, etc) times slower than hard drives and the ATA controller and the BIOS code do not know how to handle a hard drive that runs so slow. Many of the low level functions will assume that a read/write error occurred if the device does not respond within a certain period of time, but the CD-ROM drive might take several seconds just to spin the disc up to proper read/write speed before it can answer the request. As a result of this, the optical drive must be accessed by loading its own low level driver program module after the system boots up. The standard language that these "non-hard drives" attached to the ATA controller speak is called ATAPI – AT Attachment Packet Interface. The Iomega ZIP drive, some tape drives that attach to the ATA controller on the 40-wire data ribbon cable are all ATAPI devices just like the CD-ROM drives. Each however, must have its own driver in order to function properly.

  43. If signals are transmitted along a copper wire and the wire suddenly ends, the speeding electrons are not just going to disappear into nowhere. They have nowhere else to go, so they will reflect off of the end of the wire and come back down the wire in the opposite direction. In high speed data lines, the slight delay in their round trip to the end of the wire and back makes them arrive when the next bit would have arrived and they are interpreted as the next bit, or interfere with the actual next bit and ruin the actual data transmission on the wire. To prevent this from happening, the ends of the cable wires must be terminated which means attaching a resistor to the end of the wire and the other side of the resistor is attached to ground. This gives the electrons a place to go so that they will not reflect back down the wire and ruin the rest of the data. With the controller always at one end of the wire, it always terminates the wires at that end, and the other two devices can send test pulses on the cable to determine where they are situated on the wire (in the middle between the two other devices or at the far end). More than two additional devices besides the controller and this becomes technologically very difficult to do. Even though it is nice that it happens automatically, the technician should be aware of the fact that the drives automatically determine where they are located along the cable and will automatically terminate the individual signal lines where they need to be terminated.

Installation of a Single New Hard Drive

  1. Reboot to the student diskette and deploy it. (Select choice "2" from the boot menu). At the K: prompt:

    K:\>·zap 0
    ZAP Version 1.0c 05/02/96
    All Data on Fixed Disk Will Be Unrecoverable,
    Are You Sure You Want to ZAP Physical Fixed Drive 0 (Y/N)?

    To get the first character of "ZAP's" name (an ASCII "bullet") you must do the following: 1) be sure that the num lock light is on (if not press the numlock key), 2) Press and hold the [Alt] key, 3) type [2] then [5] then [0] on the numeric calculator key pad on the right side of the keyboard, 4) release the [Alt] key and the "bullet" will appear. This is how to type any character from the Extended ASCII character set which starts at code 128 and goes up to 255. Any higher number will actually wrap around to zero again. So typing in [Alt]+[2][5][6] is the same as typing in [Alt]+[0] the "NUL" control character (which does nothing at the command line). At this point ZAP is issuing a warning about destroying all data on the drive. Press [Y], then [Enter]. It wil indicate that the ZAP operation is complete or issue an error code with a full screen display of what these error codes mean. ZAP is a very low level utility so if it cannot zap the drive then no other software can write to it either. It will have to be checked.

  2. Now open the case of the PC and begin taking ESD precautions. Carefully remove the power supply cable from the hard drive. This connector can be quite tight to try rocking it side to side while pulling straight back. Never pull it by the wires, they will pull right out of the connector with ease. Never twist it too far to the side because it is plugged into a plastic hole in the hard drive which can easily crack and ruin the HDD. Be careful while pulling on the connector because it can suddenly "let go" and the back of your hand could strike the case, cables or components causing damage to the PC or more importantly your hand. Now remove the data ribbon cable connector. This one is much more delicate and usually not as tight as the power cable connector. Try to pull it with both hands from both ends straight back and out of the connector. Never rock this connector because it can bend the pins in the hard drive's side of the connector which will destroy the HDD.

  3. Now remove the mounting screws and gently remove the HDD from the PC. HDD's are attached by the standard IDE cable (or 80-wire UDMA cable) to the ATA controller which is usually a part of the Pentium class motherboard's chipset meaning in Pentium machines the controller is built in to the motherboard and you will see that the ribbon cable is attached directly to the motherboard. You will also see that the cable has three connectors. One at each end and one in the middle of the cable. Obviously the cable must attach to the controller which leaves two connectors for drives. The IDE (Integrated Drive Electronics) standard specifies that a controller can access no more than two devices. This was an engineering design choice for the IDE specification and it allowed for simplicity at the functional level as well as the user level. A drive on the cable must be either drive zero or drive one, but this nomenclature is never used. Instead they have been more colorfully labeled Master or Slave, but these names mean nothing more than the drive ID number anymore. BIOS'es used to only boot to the Master drive on the Primary Controller which made the setting much more important than it is on modern systems in which the BIOS will diligently check all drives for a suitable Master Boot Record (if allowed to). However, it is still considered proper practice to make sure that the hard drive that will boot the system is the master on the primary controller channel.

  4. Before you remove the cable from the motherboard, observe that there is a "red" stripe running down one edge of the cable. This indicates which side of the cable should be lined up to Pin #1 of the connector on the motherboard (indicated y a very small "1" or an arrow or a "40" printed on the motherboard) and the drive. If you reverse the cable not only will the PC fail to recognize the drive(s) it can also damage the controller in the motherboard (effectively destroying the entire PC) and/or the drives. Make a note of which ends of the motherboard connectors align with the red stripes of the ribbon cables. Remove the cable from the motherboard and if there is a second cable in the adjacent connector remove it as well so that you can clearly see the male block pin jumper connectors on the motherboard.

  5. There are two IDE connectors on the motherboard, one for each on the EIDE ATA controllers built in to the motherboard. They are the Primary controller and the Secondary controller. On many systems the two are identical in capability and the BIOS can be set to boot from any drive attached to either controller. However, convention dictates that you should attach the hard drive from which the system will boot up as the Master HDD of the Primary controller. Often motherboards will call them (in fine print next to the connectors) IDE 0 and IDE 1 or some other abbreviation which we know is referring to the Primary and the Secondary controllers.

  6. Now remove the jumpers. These are small pieces of plastic covering small metal inserts that cross two pins and connect a circuit within a circuit board. They are small, inexpensive switches commonly used in the PC industry. These are used to determine whether the HDD is the Master or the Slave of the controller to which it is attached (by the ribbon cable). Now trade your drive with another student and begin the installation process.

  7. The complete installation process for a single new hard disk drive on a PC is:

    1. Check/Set the Jumpers - The jumper settings on EIDE drives are completely manual. There is no way to assume that the manufacturer's default setting is correct for the intended situation that the hard drive will be involved in.
    2. Attach cables - Properly and securely attach the power and data ribbon cables to the drive.
    3. Autodetect in the BIOS - EIDE included an improvement to the IDE language including the "Identify Drive" command which allows the BIOS to ask the drive for its configuration settings and to adopt them automatically.
    4. Create Partitions - These are logically defined containers that can occupy some portion or the entire hard drive, each can hold a file system.
    5. Create File System - A file system must be created within each partition so that the operating system can organize store and retrieve files within it.
  8. First you must read the printed jumper settings on the drive and set the jumpers so that the drive will be a Master. You should note that if you are using the Fujitsu's in this exercise that the jumper setting picture on the drive's is NOT correct. This is not uncommon because the manufacturers use the same picture for their entire product line and some drives circuitry changes and they "forget" to update the picture on the sticker.

  9. Here are the settings for the Fujitsu:

    And here are the correct settings (the factory sticker is wrong!):

    So if you set the jumpers according to the factory sticker for Master, it will be a master but with cylinders limited so the drive will report itself to the BIOS to be 2112MB in size. If you follow the illustration and try to set the drive to be a slave, it will actually be set as a Master without the size limitation and report itself to BIOS as 3241MB in size. Use the corrected setting illustration and set the drive to be master with the cylinder limitation which will look like the bottom right inset in the photo. Cylinder limitation jumper settings force the hard drive to act like it is smaller than it really is. This has to do with the changes of translation methods adopted through the early years of EIDE. Large drives could sometimes cause the BIOS to crash making the hard drive useless, hence the cylinder limit setting. All modern systems support all translation methods and cylinder limiting jumpers are no longer necessary.

  10. You should avoid experimenting with jumper settings because placing jumpers across pins that were not intended to be jumpered can damage the drive and even the motherboard controller. You should go online and check the settings at the manufacturers website. These are always updated and easily updated by the manufacturer versus printed materials on the drives on the shelves in warehouses.

  11. Now place the hard drive with the circuit side facing up on the bay housing and attach the power cable. Notice that it has notches to match the plug socket on the drive. Insert it firmly so that it jams all the way in very tight. Disconnecting power to a drive while it is running will almost certainly cause a catastrophic head crash effectively destroying the drive. Knowing that the heads float on a microscopic cushion of air coming off of the spinning platters means that they are very easy to crash. The average PC should never be moved, bumped or jarred while running for the same reason.

  12. Now attach the ribbon cable. By convention almost all HDD's (only extremely old original IDE/ATA-1 specification drives might differ) align the pin #1 red stripe of the data cable to be next to the power connector, while pin #40 (the opposite side of the cable) aligns into the connector on the far side from the power connector. Be sure to attach the drive to an end connector of the cable. This is only to give you freedom of movement when you attach the motherboard end. It will also get you used to attaching masters to the end of the cable which is standard on the 80-wire UDMA cable. Remember: standard 40-wire cables do not effect the drive's identification by position, this is set by jumpers AND 80-wire UDMA cables DO affect the drive identification by position and the jumpers must be set to "CSEL" or Cable Select. Now attach the other end to the motherboard again be very sure that the Pin #1 red stripe is oriented correctly. Also be sure that you are attaching the cable to the Primary controller and NOT the Secondary controller.

  13. Now turn on the PC and observe for problematic behavior. This includes no sound from the drive. As soon as you power up the PC, the drive will initialize its controller circuitry and spin up the platters. If it does not do this, immediately turn the PC off and check all connections including the data cable. If this persists listen closer the drive might either be remarkably quiet or damaged, you can usually hear it thrashing or even sparking or sizzling faintly. Also smell for burning circuitry which has a peculiar unmistakable aroma. If you smell this at any time while working on a PC immediately shut it off. Whatever circuit burned, it will sooner or later result in a complete failure of the system. You are only trying to limit the damage to one component instead of frying the entire system.

  14. If the drive sounds active including the performance of a stepper motor sweep, the characteristic chatter or cooking popcorn sounds of hard drives, then press and hold the [Delete] key until the BIOS Setup Utility starts up its Main Menu screen:

    ROM PCI/ISA BIOS (2A59IH2H)
    CMOS SETUP UTILITY
    AWARD SOFTWARE, INC.

          STANDARD CMOS SETUP
          BIOS FEATURES SETUP
          CHIPSET FEATURES SETUP
          POWER MANAGEMENT SETUP
          PNP/PCI CONFIGURATION
          LOAD BIOS DEFAULTS
          LOAD SETUP DEFAULTS
          INTEGRATED PERIPHERALS
          SUPERVISOR PASSWORD
          USER PASSWORD
          IDE HDD AUTO DETECTION
          SAVE AND EXIT SETUP
          EXIT WITHOUT SAVING
          

     Esc : Quit
     F10 : Save & Exit Setup

          : Select Item
     (Shift)F2 : Change Color


    Time, Date, Hard Disk Type...

    Use the arrow keys between the "QWERTY" side and the numeric keypad of the keyboard to move the menu highlight to "IDE HDD Autodetect" and press [Enter]:

    ROM PCI/ISA BIOS (2A59IH2H)
    CMOS SETUP UTILITY
    AWARD SOFTWARE, INC.


       HARD DISKS      TYPE  SIZE  CYLS  HEAD  PRECOMP  LANDZ  SECTOR  MODE
      
       Primary Master:                


    Select Primary Master   Option (N=Skip) : N
     
    OPTIONS
    SIZE
    CYLS
    HEAD
    PRECOMP
    LANDZ
    SECTOR
    MODE
     
     
    2(Y) 
    2112
    1023
    64
    0
    4091
    63
    LBA
     
     
    1
    2112
    4092
    16
    65535
    4091
    63
    NORMAL
     
     
    3
    2112
    1023
    64
    65535
    4091
    63
    LARGE
     


    Note:Some OSes (like SCO-UNIX) must use "NORMAL" for install



    | ESC : Skip |


  15. Each BIOS Setup program is a little different. For the generic Award BIOS in this exercise, it should already be looking for the Primary Master drive. If the BIOS autodetection process returns all zeros at this screen then you have connected the cables or configured the jumpers incorrectly. You may immediately turn the PC off and check the jumpers and cable connections. Be very observant and be very sure that none of the cables are reversed.

  16. If the BIOS autodetection process returns numbers like you see in the example above then the primary Master has been detected and it is displaying what the drive reports itself to be. The autodetect process also offers you three separate choices and wants you to decide. The choices are concerning the method by which the BIOS will access the drive's geometry. You have already learned that drives store information in sectors which are sections of tracks. Stacks of tracks are called cylinders and each platter has its own read/write head. BIOS'es have three (now they have added two more!) methods of translating the number of cylinders, heads, and sectors/track that a drive has. These methods will be discussed in a future module. For now accept the default offer which should be LBA - Logical Block Addressing. On this BIOS it actually means "LBA Assisted ECHS" translations, but as you can see the column is not wide enough to write all of that. This is the best translation method for any drive that exceeds 504MB in size. Proceed to autodetect the Primary Slave (should be all zeros, or none, etc) accept the default offer. Do the same for the Secondary Master and Slave. Note that even if the CD-ROM drive is attached that it will return all zeros as if there were no drive. This is correct on older BIOS'es because the drive is not IDE (a hard drive) but ATAPI (AT Attachment Packet Interface) which means that it is compatible with the ATA controller only with the proper low level device driver support.

  17. Now from the Main Menu highlight the Advanced BIOS Settings option and press [Enter]. Move the highlight down to the "Boot Sequence" choice and then use the [+] or [-] keys to change the sequence until it says "A,C,CDROM" (it doesn't matter what the third choice is on your BIOS as long as the first two are "A" then "C"). Now press [Esc] to return to the Main Menu.

  18. Now from the Main Menu select Save and Exit. And the PC will automatically reboot and the changes that you have made to the drive configuration settings will now take effect. When installing a new HDD this process must be done so that the PC's BIOS will not "assume" that the old hard drive is still there and attempt to access it with the other drive's geometry. This may even appear to function but it can result in catastrophic data loss if you perform any low level disk maintenance operations like scandisk, or if you use low level data backup software like Norton Ghost, or if someone enters the BIOS and autodetects the hard drive then the parameters will be reset to the correct settings. If that is done then the translations have changed and all existing data will be scrambled in positions on the disk effectively destroying it. There is no way to undo in most BIOS CMOS settings changes either.

  19. Now boot to the student disk and deploy it. The drive is still completely empty so even though the BIOS has now configured it, it still will get no drive letters assigned to it and it still will not boot to an operating system until these structures are created on it. Let's start with the drive letters. The PC is a very modular general purpose computer such that its method of using the hard drive as a storage device does not depend on the hard drive itself which would force OS designers to adhere to logical hard drive accessibility designed by the BIOS makers. Instead the BIOS will search for a partition table written to the very first sector of the drive. This is located (using classic geometry) at Head=0, Cylinder=0, sector=1. This sector is called the hard drive's Master Boot Record. The partition tables are one important structure within this sector along with the Boot Signature, and OS Boot strap loader program all of which reside in the Master Boot Record. If any of these components get corrupted the drive will become inaccessible and all data on it is likely unrecoverable.

  20. Each OS has its own method of defining partitions on the physical device, but the partition definitions themselves are in a fixed standard location within the MBR and contain fixed standard locations for each piece of data about the partition. The BIOS will recognize up to four independent partition definitions on a single hard drive in the MBR. One of which must be marked "Active". This means that the BIOS boot strap loader process will allow the contents of this partition to attempt to boot up the system. Note that if one of the partitions defined in the MBR is not set active the BIOS will see the partition table and record the valid accessible drives but it will not boot from the drive. If there are no other drives attached to the system for the BIOS to boot from it will report a BIOS boot failure when the only thing missing is the active partition marker within the partition table which happens to be one single bit.

  21. The Microsoft DOS/Windows 9x family of operating systems all use the same basic partition layout which is an extension of the basic BIOS partition functionality. The Microsoft operating systems can write either one or two independent partition structures into the MBR. These are called the Primary DOS partition and an optional Extended DOS partition. Even Windows 9x uses these names. These operating systems include a special utility for creating these structures in the MBR called fdisk. While fdisk will create the contents of the MBR that is all that it will do. Once the partitions have been defined by fdisk as valid partition tables within the MBR, the partitions must be formatted. In the early days, the format operation actually rewrote fresh intersector gaps along all of the tracks on all of the platters of the drive. In modern drives using ZBR, doing this would be disastrous since there is no way to create the cross reference table built into the drive the format would be pie sliced again losing up to 2/3 of the drive's storage capacity in the process. Modern formatting programs simply ask the drive to verify the sectors. But they do create the VBR - Volume Boot Record which is the first physical sector within the defined partition. In DOS/Windows this holds the DPB - Drive Parameter Block which maps the locations of the FAT - File Allocation Table and the root directory. The location of these two additional hidden file system structures (the VBR being the first hidden file system structure) are needed in order for the file system drivers of the operating system to be able to find the reference to the file (in the directories starting from the root) and then cross reference the entry to the occupied sectors using the FAT.

  22. To complete the installation of the single new hard disk drive would require booting to a bootable floppy diskette or CD-ROM and executing a partitioning utility like fdisk, and then a formatting utility like format. Both actions are software and will be covered in the A+ Software portion of the certification program.

Review Questions

  1. What was the first mass storage device used with the first IBM PC? (Be specific, which of the four particular types discussed in this lecture was it?)


  2. This type of storage technology has recently become deprecated meaning that it is still

    _____________________, but will no longer be _____________________ or

    _____________________ in the future.

  3. Many of the latest motherboards do not feature an integral _____________________

    ___________________ ____________________ but some of these have a BIOS that allows

    the system to boot from an external ________ floppy disk drive as if it were a standard one.

  4. A floppy diskette physically is a single disk of _________________ storage material similar to

    that used in _________________ tapes.

  5. The floppy drive is the only common storage device in which the read/write/erase heads make

    physical _________________ with the diskette which will cause _________________ on both

    the _________________ and the _________________ making the floppy drive and the

    diskettes the _________________ reliable form of data storage for the PC.

  6. Failing diskette drives should be replaced instead of cleaned for two reasons:







  7. The original floppy drive on the IBM PC was a ___________________________ with a

    maximum data transfer rate of __________________________.

  8. The first 3 ½" floppy disk drive was developed by __________________ and had a capacity of

    _______________ and a maximum transfer rate of _________________.

  9. Because the original 5 ¼" 360KB floppy drive and the new 3 ½" 720KB floppy drives had the

    same transfer rate they could be attached to the same ______________.

  10. Since the PC was so dependent on the floppy drive, the FDC evolved from being an expansion

    card to being built directly into the ___________________.

  11. The 3 ½" 1.44MB floppy drive could not be installed directly on older systems as an upgrade

    because the _________________________ in the system did not support the data transfer

    rate of _________________ that these drives run at.

  12. Why did the IBM 2.88MB 3 ½" floppy drive and disks fail to become a standard?




  13. The read/write/erase head assemblies are attached to a ________________ arm that is

    positioned over a particular track by the _________________ motor.

  14. Looking over the floppy drive table above, which is the only floppy drive and diskette with 40 tracks? How many tracks do all of the others have?


  15. Looking over the floppy drive table above, which is the only floppy drive and diskette with an odd number of sectors/track? What else is unique to this particular type of floppy?


  16. Other than the 5 ¼" 1.2MB floppy drive, what is the RPM of all of the other types?


  17. If the diskette has 18 sectors/track and each sector holds 512 bytes then how many bits/track? If the diskette rotates 300 times per minute how many bits pass under the heads per minute? Per second? Does the FDC support the same or much higher transfer rates than this?


  18. Looking down at the top of a 3 ½" 1.44MB diskette with the exposure door facing toward you, the media sense hole is in the upper:


  19. Sectors are defined along the tracks physically or logically? Explain.


  20. What four pieces of data are stored within the intersector gaps?


  21. What is the formatted data capacity of a 3 ½" 1.44MB floppy diskette in bytes? In true binary KB? In true binary MB (to two decimal places)?


  22. What is the formatted data capacity of a 3 ½" 720KB floppy diskette in bytes? In true binary KB?


  23. Old floppy drives attached the spindle motor to the hub clamp with a ____________. In modern

    drives the drive shaft attaches directly to it and it can automatically make minor adjustments to

    maintain the correct _______________.

  24. Name 3 settings in the BIOS Setup Utility that affect the drives (FDD's and HDD's):








  25. Name 3 settings in the BIOS Setup Utility that affect the ability of the system to boot from a floppy diskette:








  26. Describe the floppy data cable include (number of wires, Pin #1, the twist and what it does):








  27. Name three ways Pin #1 could be indicated on the floppy drive male IDC connector:








  28. The standard power connector for the 3 ½" floppy disk drive is larger or smaller than that used by the hard disk drive? How many wires does it have? These wires trace back to where?


  29. The modern 3 ½" diskette is said to have a "formatted" capacity of 1.44MB. What does this mean? What occupies the rest of the "raw" 2.0MB capacity and why is this capacity almost never referred to?


  30. If the data ribbon connector is attached loosely to the diskette male block pin jumper connector and the vibration of the drive causes the connector end opposite to Pin #1 to loosen, what possible strange effect could occur? Describe it.





  31. If a system is suffering from the "phantom drive" effect, how can a second diskette still be used safely anyway?


  32. What was the first type of hard drive and controller to be manufactured specifically for the IBM PC? What was it often and incorrectly called? What was the expansion bus that this technology would attach to in order to interface to the system?


  33. What was the first IBM personal computer to actually include the hard drive as a standard component?


  34. What was the formatted storage capacity of the first generation of hard drives used on the PC?


  35. The expansion card controller brought its own BIOS code for accessing the hard drive, this would later be integrated into what two critical software packages?


  36. Describe the main problem with the ST-412 technology.





  37. Name an early technology intended to create a universal interchangeable hard drive system, and describe why it failed.





  38. What was the main accomplishment of the true IDE hard drive that makes it movable from one system to another without any problems?


  39. Early attempts at IDE attached the hard drive directly to a reduced pin count connection to what bus? How many pins were used? What were these drives called? Describe their main flaw and the reason the technology was dropped.








  40. Once the manufacturers realized that they would have to separate the IDE drive from the ISA bus with circuitry, what component was developed? How many generations of these were there? What two technologies still exist that are replacing them now and which one is the current hard drive storage standard for end-user PC's?


  41. All of the heads of the hard drive are mounted to a single assembly that positions them with a:


  42. The hard drive heads never actually touch the surface of the platters except in specially designed regions called:


  43. If the heads do ever touch the magnetic storage surface of the platters what is this event called and what is the result of it?


  44. How far off of the surface of the platters are the hard drive read/write/erase heads suspended while they ride on the air cushion created by the high speed of the spinning platters?


  45. Hard drives are manufactured in completely dust and particle free environments called:


  46. Hard drives activate how many read/write heads at a time?


  47. A hard drive's geometry is expressed in what three quantities?


  48. Cylinders are numbered from ________________ to the highest one, heads are numbered from

    ________________ to the highest one, but sectors are numbered starting with ________________

    up to the highest one.

  49. All of the _________________ of the same number, together form a cylinder.

  50. What four pieces of information are needed within the intersector gaps in order for the drive to be able to access a particular sector?








  51. In early drives intersector gaps could be rewritten by performing what kind of format operation? In modern drives why is this no longer done? What does the format command actually do on a modern drive?








  52. Modern drives can hold many times more cylinders of data than older ones due to what major technological advance? Describe it.








  53. Even while sitting idle the HDD will suddenly chatter into life for a brief period of activity and then go idle again. Describe what the drive is doing.





  54. What is used to calculate the capacity of a hard drive?


  55. Give the formula for calculating the HDD's capacity in bytes:


  56. Give an alternative that yields the HDD's capacity in KB:


  57. What is the capacity in bytes, KB and true binary MB of a hard drive with 1024 cylinders, 16 heads and 63 sectors/track? What would the hard drive manufacturer claim the capacity of this drive to be? Why is it inflated?


  58. What is the actual capacity of an HDD in a box that says "40GB EIDE Hard Drive"? (in bytes, KB, MB, and GB) What is the difference in bytes, KB, MB, and GB between the actual capacity and the claimed capacity of this drive?


  59. What is the geometric coordinate of the Master Boot Record sector?


  60. What pure software change was made to the EIDE controller onboard the hard drive that made it instantly capable of storing 2 to 3 times as much data? Describe the problem that this technology introduced.





  61. Describe the solution to the ZBR problem that is now used by all modern drives.


  62. As of ATA-2 what are the standard assigned geometry values that a hard drive should report to the system?


  63. Because of this standard assignment it is easy to calculate a rough estimate of the size of a hard drive based on the number of cylinders. What is the rough capacity of a drive with 80,000 cylinders (in MB and GB)?


  64. Based on the above estimated size calculation, roughly how many cylinders would a 120GB HDD report to the system?


  65. While the low level device ID's of two drives on the same cable are really drive #0 and Drive #1 what are they actually called? Explain the origin of these terms for the drive ID numbers.


  66. To install a new HDD the jumper settings can be assumed to be correct. T or F Why? What are the three possible Device ID jumper settings discussed in this lecture?


  67. If a drive is using a UDMA mode faster than _______MB/sec, then it must be attached using a

    ________-wire/________-pin data ribbon cable also called a ________ cable.

  68. What is the maximum number of devices that a single ATA controller can access?


  69. What is the maximum number of connectors that would be found on an ATA/IDE data ribbon cable?


  70. A single ATA-2 controller peripheral device would support how many data ribbon cables?


  71. EIDE data ribbon cables attach to connectors that are often mistakenly called the

    ______________ controller and the _______________ controller. What is the total number of devices that can be attached to the controller?


  72. Any device other than a true HDD attached to the ATA controller will use what language to communicate with the system? Give three examples of such devices.


  73. ATAPI devices cannot be accessed unless what program module is loaded?


  74. Explain the electrical signaling function that all ATAPI/(E)IDE devices perform automatically when attached to the cable.


  75. Name the three hidden structures within the partition that are necessary for the PC to boot up and be able to locate files:


  76. Name the three structures that reside within the Master Boot Record of the hard drive and what each does:




  77. How many IDE/ATA controllers (channels) were defined by the specification?


  78. What is the name of each controller (channel)?



  79. How many IDE/ATAPI devices does each controller (channel) support?


  80. What is the name of each device on an ATA channel?


  81. Explain the two different methods of setting the identification of a drive on the cable.



  82. Explain how to orient the data cable when attaching it to the hard drive connector.


  83. Explain how to orient the data cable when attaching it to the motherboard.


  84. Aside from physical mounting to the case, what are the five steps to installing a new single hard drive to the PC:






  85. What is the name of the process you perform in the BIOS to accomplish that phase of the installation?


  86. What is the name of the utility that can create partitions for DOS/Windows?


  87. How many wires are in the standard IDE cable? _____ the UDMA IDE cable? _____

  88. Which one of the HDD data cables determines the identification of the drives based on which connector they are attached to?


  89. What does the "red stripe" on the IDE data cable mean?


  90. Where is the MBR located on the drive:


  91. The bootable partition must be what type?


  92. It should be located on which drive of the controller?


  93. It should be attached to which controller?


  94. How do you change the order of the drives that the BIOS will try to boot from?


  95. The PC can still boot if you do not set the active partition. True or False.

  96. In modern systems what hard drive jumper setting is no longer necessary?


  97. In modern systems what BIOS translation method for the hard drive is the best one to use?


  98. A file system must reside within what on the hard drive? What is the minimum number of these needed on a hard drive in order to use it to store data? What is the maximum number of these that the BIOS can recognize? Where are these defined on the hard drive?


  99. A partition starts with a sector called the:


  100. EIDE drives can be autodetected in the BIOS because of what command that was added to the IDE language?


  101. An "ATA66" hard drive has what DTR? What type of data ribbon cable will be necessary for it to run at its maximum speed? Is this cable needed for an "ATA33" hard drive?


  102. You intend to install a single new hard drive into a PC. What ATA controller channel should it ba attached to? What should the drive ID be set to? What type of partition will be needed?


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