H.D.D
(Hard Disk Drive)

The hard disk drive is the main, and usually largest, data storage device in a computer. The operating system, software titles and most other files are stored in the hard disk drive.
Alternatively referred to as a hard disk drive and abbreviated as HD or HDD, the hard drive is the computer's main storage media device that permanently stores all data on the computer. The hard drive was first introduced on September 13, 1956 and consists of one or more hard drive platters inside of air sealed casing. Most computer hard drives are in an internal drive bay at the front of the computer and connect to the motherboard using ATA, SCSI, or a SATA cable and power cable. 

Types of Hard Drive

1. SCSI (Small Computer System Interface)
2. IDE (Integrated Drive Electronic)
3. SATA (Serial Advanced Technology Attachement)





SCSI Hard Drive:

50 Pin SCSI - the "standard" SCSI drive that you're most likely to see if the drive is smaller than 18GB, and didn't come out of something requiring ultra-wide. If you're looking at a beige Macintosh, an earlier SUN, SGI, or other "high-end" workstation, then chances are you'll come across a 50pin SCSI drive in the 40Mb to 4GB range. If it's really an old machine with SCSI, yes, the drive might be a 5.25 full height device that sounds like a jet-engine when it spins up.


68 Pin SCSI - Most fast/wide drives are 68 Pin. Many external drive cases for later Sun systems and other high-end devices used 68-pin connections internally and externally. They can be adapted to 50 pin, but that adapter is cumbersome and doesn't allow the drive to be placed into a 3.5 inch drive bay because the adapter juts out from the rear of the drive.

 
PinNameDirDescription
2DB0<->Data Bus 0
4DB1<->Data Bus 1
6DB2<->Data Bus 2
8DB3<->Data Bus 3
10DB4<->Data Bus 4
12DB5<->Data Bus 5
14DB6<->Data Bus 6
16DB7<->Data Bus 7
18PARITY<->Data Parity (odd Parity)
20GND---Ground
22GND---Ground
24GND---Ground
26TMPWR<->Termination Power
28GND---Ground
30GND---Ground
32/ATN<--Attention
34GND---Ground
36/BSY<->Busy
38/ACK<--Acknowledge
40/RST<->Reset
42/MSG-->Message
44/SEL<->Select
46/C/D-->Control/Data
48/REQ-->Request
50/I/O-->Input/Output
Note: Direction is Device relative Bus (other Devices).
All odd-numbered pins, except pin 25, are connected to ground. Pin 25 is left open.
 

SCSI Differential

 
PinNameDirDescription
01GND---Ground
02GND---Ground
03+DB0<->+Data Bus 0
04-DB0<->-Data Bus 0
05+DB1<->+Data Bus 1
06-DB1<->-Data Bus 1
07+DB2<->+Data Bus 2
08-DB2<->-Data Bus 2
09+DB3<->+Data Bus 3
10-DB3<->-Data Bus 3
11+DB4<->+Data Bus 4
12-DB4<->-Data Bus 4
13+DB5<->+Data Bus 5
14-DB5<->-Data Bus 5
15+DB6<->+Data Bus 6
16-DB6<->-Data Bus 6
17+DB7<->+Data Bus 7
18-DB7<->-Data Bus 7
19+DBP<->+Data Bus Parity (odd Parity)
20-DBP<->-Data Bus Parity (odd Parity)
21DIFFSENS????
22GND---Ground
23res-Reserved
24res-Reserved
25TERMPWR<->Termination Power
26TERMPWR<->Termination Power
27res-Reserved
28res-Reserved
29+ATN<--+Attention
30-ATN<---Attention
31GND---Ground
32GND---Ground
33+BSY<->+Bus is busy
34-BSY<->-Bus is busy
35+ACK<--+Acknowledge
36-ACK<---Acknowledge
37+RST<->+Reset
38-RST<->-Reset
39+MSG-->+Message
40-MSG-->-Message
41+SEL<->+Select
42-SEL<->-Select
43+C/D-->+Control or Data
44-C/D-->-Control or Data
45+REQ-->+Request
46-REQ-->-Request
47+I/O-->+In/Out
48-I/O-->-In/Out
49GND---Ground
50GND---Ground
Note: Direction is Device relative Bus (other Devices)
-Control or Data

IDE Hard Drive:

IDE (Integrated Drive Electronics) is a standard electronic interface used between a computer motherboard's data paths or bus and the computer's disk storage devices. The IDE interface is based on the IBM PC Industry Standard Architecture (ISA) 16-bit bus standard, but it is also used in computers that use other bus standards. Most computers sold today use an enhanced version of IDE called Enhanced Integrated Drive Electronics (EIDE). In today's computers, the IDE controller is often built into the motherboard.
IDE was adopted as a standard by American National Standards Institute (ANSI) in November, 1990. The ANSI name for IDE is Advanced Technology Attachment (ATA). The IDE (ATA) standard is one of several related standards maintained by the T10 Committee.
Integrated Device Electronics. It is the most widely-used hard drive interface on the market. The fancy name refers to how the IDE technology "integrates" the electronics controller into the drive itself. The IDE interface, which could only support drives up to 540 MB has been replaced by the superior EIDE (Enhanced-IDE) technology which supports over 50 GB and allows for over twice as fast data transfer rates. The other most common hard drive interface is SCSI, which is faster than EIDE, but usually costs more.

PinNameDirDescription
1/RESET-->Reset
2GND---Ground
3DD7<->Data 7
4DD8<->Data 8
5DD6<->Data 6
6DD9<->Data 9
7DD5<->Data 5
8DD10<->Data 10
9DD4<->Data 4
10DD11<->Data 11
11DD3<->Data 3
12DD12<->Data 12
13DD2<->Data 2
14DD13<->Data 13
15DD1<->Data 1
16DD14<->Data 14
17DD0<->Data 0
18DD15<->Data 15
19GND---Ground
20KEY-Key
21n/c-Not connected
22GND---Ground
23/IOW-->Write Strobe
24GND---Ground
25/IOR-->Read Strobe
26GND---Ground
27IO_CH_RDY<-- input/ output channel ready
28ALE-->Address Latch Enable
29n/c-Not connected
30GND---Ground
31IRQR<--Interrupt Request
32/IOCS16?IO ChipSelect 16
33DA1-->Address 1
34n/c-Not connected
35DA0-->Address 0
36DA2-->Address 2
37/IDE_CS0-->(1F0-1F7)
38/IDE_CS1-->(3F6-3F7)
39/ACTIVE-->Led driver
40GND---Ground

 SATA Hard Drive:

Serial Advanced Technology Attachment, often abbreviated SATA or S-ATA, is a serial link - a single cable with a minimum of four wires creates a point-to-point connection between devices. As an evolution of the older Parallel ATA physical storage interface, SATA host-adapters and devices communicate via a high-speed serial cable.
 Serial ATA (SATA, is a computer bus technology designed for transfer of data to and from a hard disk. It is the successor to the legacy Advanced Technology Attachment standard (ATA, also known as IDE). This older technology was retroactively renamed Parallel ATA (PATA) to distinguish it from Serial ATA. This interface uses 7-pin cables for the data connection, and transmits the data serially rather than in parallel. In addition, Serial ATA should give users the ability to hot swap hard drives. This adds a capability that more expensive systems such as SCSI and Fibre Channel have had for a long time, though the future will tell how widely users exploit that aspect of the technology. Serial ATA also reduces the signalling voltage from the 5 volts used in P-ATA down to 0.5 volts, which reduces power consumption and electrical interference.
Due to serial transfer and lower power the maximum allowable length of SATA cables exceeds that of ATA ribbon cables
The Serial ATA (SATA) bus is defined over two separate connectors, one connector for the data lines and one for the power lines (SATA power pinout). A Serial ATA Hard drive may also have a third connector for legacy PATA power connections. The PATA power connector used instead of the SATA power in some early devices
Physically, the SATA power and data cables are the most noticeable change from Parallel ATA. The SATA standard defines a data cable using seven pins to supply four conductors shielded with ground supplied by the other three pins.
 
PinNameFunction
1GNDGround
2A+Transmit+
3A-Transmit-
4GNDGround
5B-Receive-
6B+Receive+
7GNDGround
The SATA standard specifies a power connector sharply differing from those used by PATA drives and many other computer components. It is wafer-based, 15-pin shape. The seemingly large number of pins are used to supply three different voltages — 3.3 V, 5 V, and 12 V
Each voltage is supplied by three pins ganged together (and 5 pins for ground). This is because the small pins cannot supply sufficient current for some devices. One pin from each of the three voltages is also used for hot plugging. The same physical connections are used on 3.5-inch and 2.5-inch notebook hard disks.
PinSignal PSU Color Wire
1+3.3VDC orange
2+3.3VDC orange
3+3.3VDC orange
4GND black
5GND black
6GND black
7+5VDC red
8+5VDC red
9+5VDC red
10GND black
11Optional black
12GND black
13+12VDC yellow
14+12VDC yellow
15+12VDC yellow
Pins 3,7,13 are pre-charge.
Pin 11 can be used for activity indication and/or staggered spin-up.
Pins 1, 2, and 3 are optional as well, as evidenced by some adapter cables that connect the drives to older PSUs. These are usually Y-adapters that have the four-pin drive connector on the other end. Currently, SATA drives rarely use 3.3 volts. That may be because there are too many people using adapters so the drive makers don't want the headaches which come with using 3.3 volts. But in the future, 3.3 volt drives may become common so you need to be careful when using SATA power cables which don't implement 3.3 volts.

 SCSI Hard Driver Interface Cable & Power Connector



IDE Hard Driver Interface Cable & Power Connector



SATA Hard Driver Interface Cable & Power Connector




 

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