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Hard Disk الصلب القرص

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Construction of the Hard Disk

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Tracks and Sectors

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The Difference Between Tracks and Cylinders

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Platter SizeA platter from a 5.25" hard disk, with a platterfrom a 3.5" hard disk placed on top of it forcomparison. The quarter is included for scale (andstrangely, fits right in the spindle hole for bothplatters... isn't that a strange coincidence ?

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Hard Disk Operational Overview

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Platter Diameter

Typical Form FactorApplication

5.125.25"Oldest PCs, used in servers through the mid-1990s and some retail drives in the mid-to-late 1990s;

now obsolete

3.743.5"Standard platter size for the most common hard disk

drives used in PCs

3.03.5"High-end 10,000 RPM drives

2.52.5 ,"3.5"Laptop drives (2.5" form factor); 15,000 RPM drives

(3.5" form factor)

1.8PC Card (PCMCIA)PC Card (PCMCIA) drives for laptops

1.3PC Card (PCMCIA)Originally used on hand-held PCs (no longer made)

1.0CompactFlashDigital cameras, hand-held PCs and other consumer

electronic devices

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Read/Write Heads A pair of mated head sliders with their platter removed.You can see that the tension of the head arms has causedthem to press against

each other .

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Hard Disk Read/Write Head Technologies

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القرص سطح

This illustration gives you some idea of just how small the flyingheight of a modern hard disk is (and today's hard disks have

flying heights significantly lower than 3-7 millionths of an inch !

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Hard Disk Head Sliders, Arms and Actuator

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Hard Disk Connectors and Jumpers

Some of the connectors and jumper pins on a3.5", 36 GB, 10,000 RPM SCSI Cheetah

drive .

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Connectors Types

•IDE Connectors

•SCSI Connectors

•SATA Connectors

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IDE Connectors

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SATA Connectors

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SCSI Connectors

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Data Interface Connector

A standard hard disk IDE/ATA data interface connector.If you look closely you can see markings for pins #1, #2, #39 and #40.A 50-pin SCSI interface connector looks identical except that ithas 25 columns of pins instead of 20 (they look so much alike thatgetting the two mixed up is common). A 68-pin SCSI interface

connector is pictured on the parent page of this page

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IDE/ATA Configuration Jumpers

Jumper block for an IDE hard disk.The jumpers are labeled "MA" (master),"SL" (slave) and "CS" (cable select). OtherIDE drives will have slightly differentjumper configuration or

placement .

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Jumpers

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Hard Disk Logic Board

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Hard Disk Cache and Cache Circuitry

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Cache SizeThe cache chip from a Seagate Barracuda hard disklogic board. This chip is the entire cache: it's a 4 Mib chip,which is 512 kiB, the size of the cache on this drive. Somecaches use more than one chip, especially the larger

ones .

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Removable Hard Disk Trays