Auto Cad Book.pdf

Lesson 8 : Hard Disk Drive Interface 

8.1. Learning Objectives On completion of this lesson you will be able to describe:
 What is hard disk drive interface
 Different types of hard disk drive interface.

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8.2. Introduction to Drive Interface 

Drive interface is the world wide predefined standard by which a controller can talk to its drive. This standard defines the cable and connectors between the controller and the hard disk and the language by which they talk together. We can get controllers from different industries and also hard disk drives from different industries. But there is no problem because of the interface. For example, if we connect the controller of one industry having IDE interface with a hard disk drive of another industry having IDE interface, they can work together because the interface (i.e., the language) between them is the same. Different drive interfaces are available. We have discussed here some common interfaces like ST506, ESDI, SCSI and IDE. 

8.3. ST506 

Here ‘ST’ stands for ‘Shugart Technologies’ because this interface is first defined by this industry. It has the following characteristics: 

 A 20 wire cable for data signals 

 Another 30-wire cable for control signals. 

 5 Mbps (Meg bit per second) data transmission rate 

 Supports up to 16 head disks 

 Short cable length 

 Prone to noise 

 Slower controlling method than other interfaces 

 Can not send drive information (how many platters, tracks etc.) to the controller. 

 Used in old models of computers. 

8.4. ESDI 

It is an advanced design of ST506. Some problems of ST506 interface are removed in this modified design. It has the following characteristics:

 Cabling same as ST506 (20-wires data and 34-wires control).

 Supports up to 256 head

 24 Mbps data transfer rate.

 Allows longer cables

 More noise free

 Can send drive information (how many platters, tracks etc.) to the controller.