For many years, the hard disk drive (HDD) has been the unsung hero of the PC industry – the glamour goes to the processors and graphics accelerators but where would we be without at least several Gigs of fast mass storage? Now, however, disk drives are getting smarter ... and they are no longer confined to the PC, as Laura Formenti, a Marketing Engineer for STMicroelectronics, explains.
Once dismissed by many pundits as a technology without a future, the HDD industry has succeeded, year after year, in continually increasing storage capacity and reducing cost/Gigabyte. Without the astonishing progress made by HDD manfacturers and their chip partners, the PC would still be suitable for not much more than word-processing.
However, while we can safely assume that PC users will continue to demand more and more storage capacity, this is only one part of the picture: the HDD is beginning to find its way into consumer electronics and emerging Internet appliances. In these settings, which include set-top boxes, home entertainment systems, game stations, web TV and digital video equipment, the HDD is a key enabling technology, opening up new levels of sophisticated functionality. Set-top boxes incorporating HDDs have already become available and many market analysts expect dramatic growth for this market.
The so-called personal video recorder (PVR) enables, even in its most basic form, substantial performance enhancements over video cassette recorders, both in terms of video quality and ease of use. For example, functions such as rewind and fast-forward that involve irritating delays and trial-and-error in a VCR become instantaneous in a HDD-based recorder, while a hitting the pause key results in a perfect still image.
In these new products, there is a growing need to build intelligence into the storage device itself, with the HDD becoming a smart device that serves up new functions, running application-specific software.
In network applications there is also a rapidly growing demand for storage capacity, fuelled by the explosion in digital content, the pervasiveness of network computers and the dramatic popularity of the Internet which makes it increasingly important to optimise network infrastructures with advanced storage solutions.
For example, network attached storage (NAS) is a new emerging technology that facilitates adding storage capability with a direct plug-and-play connection to the network and ensures compatibility with different networks' protocols.
The emerging new applications HDDs demand a much greater degree of on-board intelligence. The traditional HDD requires leading-edge technology to achieve the incredible positioning accuracies needed to work with today's track densities but the drive's function is a simple reactive one: the OS tells it what data it wants and the HDD retrieves it.
Smart HDDs will need to be fast and flexible, even to the extent of supporting interfaces such as Ethernet, xDSL, Bluetooth and IEEE-1394. At the same time, there will be no let-up on the pressure to keep increasing the number of Gigabytes that can be crammed onto the magnetic disks which means closer track spacing which requires, in turn, greater accuracy in positioning the read/write head.
As a leading supplier of silicon to the world's HDD makers, ST has researched the technical challenges that the industry will face and is working with leading HDD companies to develop solutions. For example, ST has introduced an innovative device that allows the effects of mechanical vibration to be corrected. Rotational vibrations cause small errors in the read/write head position which limit the spacing between adjacent tracks.
ST's L6670 is a capacitive rotational accelerometer sensor produced using micro-electro-mechanical system (MEMS) technology; vibrations of the disk drive cause tiny rotational displacements of the moving part of the MEMS structure, which are measured by sensing the small variations in capacitance that they cause. Capacitance changes as small as 0,05 femtoFarad (0,05x10e-15F) can be measured by the device.
With the L6670 it is possible to detect and measure minute rotational vibrations so that the firmware can generate a feed-forward correction signal for the voice coil drive circuit to keep the head in the correct position. This allows the track spacing to be reduced significantly, increasing the storage density per unit area. The speed performance of the drive is also improved because less time is wasted restoring the correct head position when vibration has caused the tracking to be temporarily lost.
As far as the HDD's intelligence is concerned, the 16 bit MCU that is perfectly adequate for controlling the servos today will clearly not be able to take on tasks such as encoding or decoding an MPEG video or MP3 audio stream.
The kind of processor that these applications will need is a combination of MCU and DSP, with fast context switching and single instruction multiple data (SIMD) capability for multimedia computations.
Such a processor has already been developed by ST in the form of the ST100, which delivers 2400 MOP/s and 600 megaMAC/s at 300 MHz, powered by 1,8 V. The power of the ST100 will liberate the HDD from its traditional 'dumb but invaluable' role and open up many new possibilities. HDDs will be making their presence felt in an ever increasing range of new consumer products, with many of the most important new applications enabled by technology developed by ST.
For further information about STMicroelectronic's products contact Arrow Altech Distribution (011) 923 9600, AGAtronics (011) 789 1065, Avnet Kopp (011) 444 2333 or Communica (012) 322 7613.
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