EA-194                                                       PC Systems Support

PRACTICAL –               Set-up procedure for a HDD:

THEORY: -                                             Hard Disk Drives (HDD)

Types: MFM, RLL, IDE, SCSI

 HDD Layout:

Air-tight mechanical unit

Multiple double sided disk platters (made from ? and coated with ?)

Multiple Heads on actuator arms for each side of platter (2 Heads per arm for inner platters)

HDD Data Transfer Rates and Access Times

Definitions:

Cylinders: Same as tracks per disk but generally pertains to multiple disk configurations in later HDD’s.

Head: Single read/write component attached to actuator arm that reads and writes data.

Sector: 512 Bytes. There may be more than one sector per cluster on a HDD.

Tracks: Single circular impression on a disk that is divided into sectors for storing data.

Landz: Reduction in magnetic field (flux) used to write data as the centre of the disk is approached. This is due to increased data density towards the disk’s centre. The reduced magnetic field prevents magnetic bleed that may corrupt nearby data.

Precomp: The more efficient use of disk capacity by increasing the number of sectors per track as the disk outer perimeter is approached from the centre.

Hi-Level format: Preparing a new disk for use by mapping the disk and creating tables to manage files. For DOS format (HDD’s)– creates a DOS boot record, FATs and a root directory.

Low-Level format: For HDD’s – This physically formats the HDD and creates the tracks and sectors.

Interleave: Due to access time and limited data transfer speed older HDD’s were not fast enough to access the next sector for data. Therefore, it was necessary to make the following sector 2 or more sectors away. This was called interleaving or the interleave factor. The interleave factor depended on the speed of the HDD. Current technology allows interleave factors of one (e.g. sector two directly follows sector one).

Other Features: Generally 2 IDE ports on the mainboard (IDE 0, IDE 1 or IDE A, IDE B). Each IDE port can have two IDE drives attached known as the Master and Slave. One of these may be an IDE CD ROM drive. You must use jumpers on the IDE drive to configure it as a Master or slave.

Tips: If your 2^nd HDD has been partitioned with a Primary DOS partition then it will become your "D" drive when installed with your Master HDD (The CD-ROM will always become your last drive. If you want to avoid this then partition the 2^nd HDD so that it contains only one large EXTENDED partition (you can still have up to 4 logical drives within this extended partition).

Calculating HDD Capacities: using Cylinders/Tracks, Heads & Sectors.

Formula: Capacity = Tracks x Heads x Sectors per Track x 512 Bytes

File Allocation Table (FAT): DOS file management and storage is controlled using the FAT. As you know, HDD’s contain clusters that are likely to contain more than one sector. A cluster is the smallest possible unit that can be addressed on the hard drive. Unlike FDD’s, DOS formatted HDD’s use a 16-bit (2-bytes) FAT referred to as FAT-16. This meant that the HDD FAT could hold 2 exp. 16 file entries. Therefore, the HDD could have 65,536 clusters (or files) that could be addressed.

This indicates that a 512 Megabyte HDD would have 512 MB/65536 cluster sizes. This cluster size contains many sectors (7.8 K/512). What if a file is smaller than 7.8 Kilobytes? Then it still will take up 7.8 Kilobytes of space. The unused space is referred to as slack space. This unused space, caused by small files not using the entire cluster, can reduce the effective size of the HDD. Hence, the introduction of FAT 32 for very large disk capacities.

Another option is to use FAT 16 with compression (e.g. DriveSpace). The ‘Windows 98’ FAT 32 allows single partitions greater than 2 Gigabytes. Like floppy disks, there is a 224 folder (directory) entry limit to the root directory.

LBA [Large Block (mode) Addressing]: This feature enables the system through the BIOS setup to access HDD’s with capacities over 512 MB.

HDD Types: MFM, RLL, IDE, SCSI

MFM (17) & RLL (26)

Old technology. Uses 17 to 26 sectors per track over the entire drive platter. Two cable configuration. Can be low-level formatted often to extend its service life.

IDE: Abbreviation of either Intelligent Drive Electronics or Integrated Drive Electronics, depending on who you ask. An IDE interface is an interface for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive. It is a low-cost alternative to SCSI interfaces. The original IDE interface supports data transfer rates of about 3.3 megabytes per second and has a limit of 528 megabytes per device. These numbers are comparable to what SCSI offers. To take advantage of EIDE, you need both an EIDE mass storage device and an EIDE interface installed in your computer.

Large capacity (Over 13 Gigabyte capacity) for EIDE and later.

Easy to install.

Unique drive format and data access method, therefore: a controller specific to the IDE drive must be used. Check with manufacturer before attempting a low-level format. The number of sectors per track varies as the centre of the disk is approached. Therefore, the disk density is more efficiently utilised.

Voice coil technology (after 1991).

EIDE: Short for Enhanced IDE, a new version of the IDE mass storage device interface standard developed by Western Digital Corporation. It supports data rates of between 4 and 16.6MB (megabytes) per second, about three to four times faster than the old IDE standard. In addition, it can support mass storage devices of up to 8.4 gigabytes, whereas the old standard was limited to 528MB. Because of its lower cost, enhanced IDE is expected to replace SCSI in many areas.

EIDE is sometimes referred to as Fast ATA, or Fast IDE, which is essentially the same standard, developed and promoted by Seagate Technologies.

There are four EIDE modes defined. The most common is Mode 3, which transfer data at a rate of 11.1 MBps (megabytes per second). Mode 4 supports transfer rates of 16.6MBps. Currently under development is a new mode that will support transfer rates of 33MBps.

SCSI: Abbreviation of small computer system interface. Pronounced scuzzy, SCSI is a parallel interface standard used by Apple Macintosh computers, some PCs, and many UNIX systems for attaching peripheral devices to computers. All Apple Macintosh computers starting with the Macintosh Plus come with a SCSI port for attaching devices such as disk drives and printers.

SCSI interfaces provide for faster data transmission rates (up to 40 megabytes per second) than standard serial and parallel ports. In addition, you can attach many devices to a single SCSI port, so that SCSI is really an I/O bus rather than simply an interface.

Although SCSI is an ANSI standard, there are many variations of it, so two SCSI interfaces may be incompatible. For example, SCSI supports several types of connectors.

While SCSI is the only standard interface for Macintoshes, PCs support a variety of interfaces in addition to SCSI. These include IDE, enhanced IDE and ESDI for mass storage devices, and Centronics for printers. You can, however, attach SCSI devices to a PC by inserting a SCSI board in one of the expansion slots. Many high-end new PCs come with SCSI built in. Note, however, that the lack of a single SCSI standard means that some devices may not work with some SCSI boards.

When using SCSI devices with a PC they must be installed with a SCSI controller interface card. However, multiple SCSI devices (up to 16 now) can be attached to the one controller interface adapter card. Each SCSI device must be set with its own unique ID number that corresponds to its priority level (highest priority = highest ID number). The unique ID is generally set by switches or jumpers and is the binary equivalent (e.g. ID 7 = 0111).

The following varieties of SCSI are currently implemented:

SCSI: Uses an 8-bit bus, and supports data rates of 4 MBps

Fast SCSI: Uses an 8-bit bus, and supports data rates of 10 MBps.

Ultra SCSI: Uses an 8-bit bus, and supports data rates of 20 MBps.

Fast Wide SCSI: Uses a 16-bit bus and supports data rates of 20 MBps.

Ultra Wide SCSI: Uses a 16-bit bus and supports data rates of 40 MBps.

Practical:        Hard Disk Drive Setup

Resources: HDD’s (preferably 1Gigabyte and over), PC (with Large Disk support & IDE support).

Aim: To enable students to competently install, partition and hi-level format a HDD for a PC and to use common tools to manage and maintain a HDD. Students are also expected to gain experience with SCSI devices through interaction during the teacher’s demonstration.

The following tasks are to be performed by students:

Students are expected to observe and interact during the following demonstration:

Procedure:

Step1.  Using the HDD available – set the jumper to configure the HDD as a single master. The jumper pins for this setting are generally labeled "MA".

Step 2.  Secure your HDD in the PC cavity allocated for HDD’s (Don’t over tighten screws).

Step 3.  Attach the wide ribbon IDE cable to the mainboard’s IDE slot (Ensure that you have positioned the red Striped part of the ribbon where pin #1 is located for the IDE slot and HDD. Pin #1 is generally located on the power supply connector side of the HDD).

Step 4.  Secure one of the spare power supply cables to the HDD. This can only fit one way.

Step 5.  After rechecking your connections, turn your PC "on" and enter into the CMOS settings (generally accessed by pressing the "Delete" key when prompted at start-up).

Step 6.  Using the "arrow" keys navigate to the "HDD autodetect" entry in the main menu and press "enter". Select the HDD type recommended by the auto-detection process (this will probably be the first entry in the list). Press either "Esc" or "No" for each successive HDD auto-detection.

Step 7.  Ensure that your PC boot sequence includes the FDD in the CMOS settings. If your HDD is larger than 528 MB make sure the mainboard supports larger HDD’s (i.e. you may have to enable "LBA mode" in the CMOS settings).

Step 8.  Now start your PC with your floppy boot disk and run the FDISK.EXE program (you should already have FDISK and FORMAT on your boot disk). If all went well you should be able to display your HDD’s current partition information by selecting the appropriate number from the FDISK menu. Note: If you are asked if you want to enable "Large Disk Support" choose "No".

Practical:                                          Partitioning

In this part of the practical you will:

i) Delete the current partitions

ii) Create one "Active" Primary DOS partition that is 50% of total HDD space.

iii) Create an Extended DOS partition equal to the remaining 50% of HDD space.

iv) Create two logical DOS drive partitions within the Extended DOS partition. Each of these will be 50% of the       Extended DOS partition in size.

i)  Deleting the current partitions: From the FDISK menu select number [3]. From the following menu you must delete any partitions in the following order:

First – Non-DOS partitions.

Second – Any logical DOS drives within the extended partition.

Third – The Extended DOS partition.

Fourth – The Primary DOS partition.

Note: Each time you delete a partition review the changes by using the "Display partition Information [4]" listed in the main menu.

Continue until all partitions have been deleted.

ii)  Creating an Active Primary DOS partition: From the initial FDISK menu select "Create DOS partition [1]". You will now be presented with a second menu where you will select "Create a Primary DOS partition [1]". When asked if you would like to use all of the available HDD space for the primary DOS partition – select "No". When asked to enter the amount of space you would like to allocate for the primary DOS partition in Megabytes or percentage of HDD space – enter 50%.

Note: You may now be asked whether you would like to make this partition "ACTIVE". Select "YES", keeping in mind that you are allowed to make a partition "ACTIVE" at any time by selecting it from the list in the main menu.

iii)  Creating an Extended DOS partition: Select "Create a DOS partition [1]" from the main menu again and select "Create an Extended DOS partition" from the second menu. Use all of the remaining HDD space left for this partition (this should be displayed).

iv)  Creating Logical DOS Drives within the Extended DOS partition: Select "Create a DOS partition [1]" from the main menu again and select "Create a logical DOS Drive within the Extended DOS partition" from the second menu. If prompted to use all of the available space in the extended DOS partition, say "No". When prompted to enter the amount of space you would like to allocate for the first logical DOS drive in either Megabytes or a percentage of space – enter 50%. After a moment you will be prompted for the size of your second logical DOS drive – choose the amount shown by pressing the "ENTER" key.

Before exiting FDISK ensure that your partitions are correct by selecting to display the partition information again from the main menu.

Now: escape from FDISK and reboot the PC.

Finally: format all three drives created by FDISK.