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Hard Disk Drive
by John Anthony


The Hard Disk Drive (HDD) installs in one of the 3-1/2 inch internal drive bays in the PC and is secured by machine screws.

On standard electro-mechanical drives data storage is maintained magnetically on multiple rigid disks that are stacked up like pancakes.
Small arms with magnetic pickups move rapidly back and forth across the top and bottom surface of each disk in the drive.
The sensors float just a few microns above the rotating disk surface and can read and write data (ones and zeroes) at very high rates.

In the late 2000's Solid State hard drives began to appear. They are entireley electornic and store data in flash memory.

Data between the motherboard and the hard disk drive is carried over a 40 conductor interface called IDE (Integrated Drive Electronics).
This parallel bus was later renamed PATA (Parallel Advanced Technology Attachment).
Drives with PATA interfaces are powered by a separate 4-pin cable from the power supply which carries +5v, +12v and ground.

Since 2009 SATA (Serial Advanced Technology Attachment) has effectively replaced PATA in desk-top and laptop PC's.
It is a very fast serial bus and uses only 7 lines for data transport which is huge reduction from the 40 lines PATA requires.
SATA drives use a separate 15 pin connector for power and receive +5v, +3.3v, +12v and ground from the power supply.

A 40 Gbyte (Gigabyte) drive in 2004 sold for about $100. In 2012 a 1 Tbyte (Terabyte) drive sells for the same or slightly less and has 25 times more storage capacity!
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