areal density


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areal density

[‚er·ē·əl ′den·səd·ē]
(computer science)
The amount of data that can be stored on a unit area of the surface of a hard disk, floppy disk, or other storage device.

areal density

The number of bits per square inch of storage surface. It typically refers to disk drives, where the number of bits per inch (bpi) times the number of tracks per inch (tpi) yields the areal density.

From 2,000 to 100,000,000,000 Bits
The areal density of disk storage devices has increased dramatically since IBM introduced the RAMAC, the first hard disk computer in 1956. RAMAC had an areal density of two thousand bits per square inch, while current-day disks have reached 100 billion bits (100 gigabits per square inch). Perpendicular recording is expected to increase storage capacity even more dramatically. See perpendicular recording, superparamagnetic limit, holographic storage and AFM.

Rings on Dumbbells for Denser Memory


The areal density of memory chips is much greater than that of magnetic disks. However, in 2006, the California Institute of Technology built a prototype memory chip that used molecular switches resembling dumbbells with a ring that slides along the center bar. Voltage pushes the ring from one end to the other to represent a 0 or 1. Only in the early stage of development, the first prototype chip was no larger than a white blood cell and held 160,000 bits. If it were to become commercially viable, the density would exceed 600 billion bits per square inch. In addition, scientists claimed that improvements in this technology are expected that could make the bits 10 times denser. Such an achievement would yield six trillion bits per square inch!
References in periodicals archive ?
Technical details about Seagate's landmark areal density achievement can be found at: http://www.
Marvell is pleased to have contributed to Read-Rite's ongoing success in achieving a new areal density record with our 88C4200 PRML read channel" said Dr.
Kryder estimates that the switch to perpendicular recording will occur sometime between 100 and 200 gigabits per square inch areal density.
Veeco's NEXUS PVD multi-target system is used to deposit high-quality, extremely uniform, thin film multi-layer stacks and will be used by the customer to manufacture high areal density Tunneling Magneto-Resistive (TMR) heads.
Areal density has grown at an impressive 60 percent compound annual growth rate, historically, and has accelerated to greater than a 100 percent rate since 1999.
In September, Read-Rite announced a data storage world record with the successful demonstration of GMR heads using spin valve designs capable of an areal density of 13.
In its Corporate Research labs last year, Sony provided the first demonstration of a breakthrough in tape storage areal density by achieving 6.
The areal density was achieved using available MR heads on manufacturing-ready media that is currently being shipped to customers for product qualifications.
As hard drive areal density increases, the physical dimensions of the read sensor have had to be significantly reduced to accommodate the smaller data bits.