Hard Disk Drive

Hard disk drive The hard disk drive is the primary storage location where data is permanently stored. Below is an illustration of what the inside of the hard disk drive may look like. The four main components of a hard disk drive are the platters, head arm, chassis, and the head actuator. The majorities of computer hard disk drives are permanently stored in an internal drive bay at the front of the computer and are connected with one ATA / SCSI cable and power cable. Unlike other drives, the hard disk drive is the only drive that is not physically accessed by the user like the floppy disk drive or the CD-ROM drive.

Size information The capacity of computer hard disk drives and the files it contains can be confusing. Below is a listing of the standards in different size values. It is important to realize that not all manufacturers and developers use these values. For example, a manufacturer may consider a gigabyte as the value of a gibibyte.

Bit Nibble Byte Kilobit Kilobyte Kibibit Kibibyte Mebibit Mebibyte Megabit Megabyte Gibibit Gibibyte Gigabyte Gigabit Tebibit Tebibyte Terabyte Terabit Pebibit Pebibyte Petabit Petabyte Exabyte Exabit Exbibit Exbibyte Zettabyte Yottabyte

Value of 0 or 1 4 Bits 8 Bits 1,000 bits 1,000 bytes 1,024 bits 1,024 bytes 1,048,576 bits 1,048,576 bytes 1,000,000 bits 1,000,000 bytes 1,073,741,824 bits 1,073,741,824 bytes 1,000,000,000 bytes 1,000,000,000 bits 1,099,511,627,776 bits 1,099,511,627,776 bytes 1,000,000,000,000 bytes 1,000,000,000,000 bits 1,125,899,906,842,624 bits 1,125,899,906,842,624 bytes 1,000,000,000,000,000 bits 1,000,000,000,000,000 bytes 1018 bytes 1018 bits 260 bits 260 bytes 1021 bytes 1024 bytes

INTERFACE of HDD A computer interfaces is what allows a computer to send and retrieve information for storage devices such as computer hard disk drives and CD-ROM drives. This section of Computer Hope briefly describes each of the major types of computer interfaces that are used today and that have been used in the past. In addition to a brief explanation, this page also contains technical specifications about each of the interfaces.

ATA, EIDE, AND IDE INFORMATION Today, the ATA interfaces are the most commonly used interface on IBM compatible computers to connect to computer hard disk drives, CD-ROM drives, and other types of disk drives. Each of the below standards are compatible with each other, which means a new ATA drive can be used in a computer using an older ATA specification. Finally, when a new feature was introduced in an ATA standard, that feature is also found in future releases. In other words, a ATA-4 is going to have support for PIO modes 0, 1, 2, 3, and 4, even though these were introduced in ATA-1 and ATA-2. Below is a listing of each of the ATA, IDE, and EIDE standards to help give user a better understanding of the history behind this interface as well as an understanding of each interface's capabilities.

ATA / ATA-1 / IDE ATA is short for AT Attachment interface and also more commonly known as IDE or ATA-1. ATA was approved as a standard on May 12, 1994 under the ANSI document number X3.221-1994. ATA was first developed by Control Data Corporation, Western Digital, and Compaq. ATA-1 utilizes a 8-bit or 16-bit interface, has a transfer rates of up to 8.3MBps, and has support for PIO modes 0, 1, and 2. Today, ATA / ATA-1 is now considered obsolete.

ATA-2 / EIDE / Fast ATA / Fast IDE / Ultra ATA ATA-2, more commonly known as EIDE, and sometimes known as Fast ATA or Fast IDE, is a standard approved by ANSI in 1996 under document number X3.279-1996. ATA-2 introduces new PIO modes of 3 and 4, has a transfer rate of up to 16.6MBps, DMA modes 1 and 2, LBA support, and supports drives up to 8.4GB. Today, ATA-2 is now considered obsolete.

ATA-3 / EIDE ATA-3 is a standard approved by ANSI in 1997 under document number X3.298-1997. ATA-3 added additional security features and the new S.M.A.R.T feature.

ATA-4 / ATAPI-4 / ATA/ATAPI-4 ATA-4 is a standard approved by ANSI in 1998 under document NCITS 317-1998. ATA-4 includes the ATAPI packet command feature, introduces UDMA/33, also known as ultra-DMA/33 or ultra-ATA/33, which is capable of supporting data transfer rates of up to 33MBps.

ATA-5 / ATA/ATAPI-5 ATA-5 is a standard approved by ANSI in 2000 under document NCITS 340-2000. ATA-5 adds support for UltraDMA/66, which is capable of supporting data transfer rates of up to 66MBps, and has the capability of detecting between 40 or 80-wire cables.

ATA-6 / ATA/ATAPI-6 ATA-6 is a standard approved by ANSI in 2001 under document NCITS 347-2001. ATA-6 added support for UltraDMA/100, and had a transfer rate of up to 100MBps.

ATA layout

Each of the above ATA interfaces that are used with the 3.5-inch disk drives have a 40-pin connector and are capable of supporting up to two drives per interface. However, 2.5-inch hard disk drives utilize a 50-pin connector and PCMCIA utilizes a 68-pin connector Below is an illustration of the ATA interface Pin

Function

Pin

Function

1

Reset

2

Ground

3

Data 7

4

Data 8

5

Data 6

6

Data 9

7

Data 5

8

Data 10

9

Data 4

10

Data 11

11

Data 3

12

Data 12

13

Data 2

14

Data 13

15

Data 1

16

Data 14

17

Data 0

18

Data 15

19

Ground

20

Key

21

DDRQ

22

Ground

23

I/O Write

24

Ground

25

I/O Read

26

Ground

27

IOC HRDY

28

Cable Select

29

DDACK

30

Ground

31

IRQ

32

No Connect

33

Addr 1

34

GPIO_DMA66_Detect

35

Addr 0

36

Addr 2

37

Chip Select 1P

38

Chip Select 3P

39

Activity

40

Ground

ATAPI Short for AT Attachment Packet Interface, ATAPI is an extension to ATA which allows support for devices such as CD-ROM drives, Tape drives and other computer peripherals and not just hard disk drives. Before the release of ATA-4 or ATA/ATAPI-4, ATAPI was a separate standard from ATA.

SERIAL ATA (SATA) Shot for SerialATA, SATA 1.0 was first released in August 2001 and is a replacement for the Parallel ATA interface used in IBM compatible computers. SerialATA is capable of delivering 1.5Gbps (150MBps) of performance to each drive within a disk array, offers backwards compatibility for existing ATA and ATAPI devices, and offers a thin small cable solution as seen in the below picture. This cable helps make a much easier cable routing and offers better airflow in the computer when compared to the earlier ribbon cables used with ATA drives.