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Hard Drives: How They Work (Page 4/4)

Posted: April 17, 2000
Written by: Tuan "Solace" Nguyen

Head Types:

Ferrite Heads: Early hard drives used read/write heads that were constructed of a thin copper wire that was wound around a small ferrite core with a tiny cut out of it. This cut determined the size of the data bits that could be written to disk and read from disk. An electrical signal would be sent through in one direction or the other causing electrical induction. This creates specific patterns of magnetic fields arranging magnetic particles on the platter to either face north or south. When reading from the disk, the head senses which direction a particle is in, translating that into a 0 or 1 bit.

Thin-film Inducted Heads: This type of head was developed by IBM in 1979. The heads used photolithographic techniques from semiconductor manufacturing processes to create the head structures. The magnetic core and the coil were created the same way. This gave a greater precision than the Ferrite design and allowed for more bit read and write accuracy.

Magneto-resistive Heads: These types of heads use separate read and write components for even greater precision than thin-film inducted heads. The read component is made of a thin-film material that changes its resistance when near a magnetic field (being the bits). This produces a stronger signal that enables greater areal density limits and thus allowing more bits to be crammed into a platter.

Giant Magneto-resistive Heads: This technology is based on magneto-resistive heads with different thin-film materials that produced large amounts of magneto-resistance. That is where the term “giant” comes from – the giant amounts of resistance. In 1997, IBM introduced the GMR heads which replaced the MR heads with different elements and increased areal densities by many times. They are used in today’s high-end hard drives.


Traditionally, hard drives are based on either IDE (Integrated Drive Electronics) or SCSI (Small Computer System Interface) interfaces. We’ll dive into the world of interfaces in the sequel to this article. But for now, we hope this "How It Works" guide has helped you to understand the fundamentals of hard drive technology. :) Heh, wait until we tell you about solid-state hard drives. Until next time…

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