For professional audio and video work, any gaps in data flowing from the hard drive can cause dropped video frames, jerky motion, annoying sound pauses, or even software crashes. A pause in writing a recordable CD-ROM renders the disc useless. In its AV line, Micropolis uses a variety of tricks and technologies--some proprietary, some not--to guarantee an uninterrupted data flow. Most recent hard drives use some of these techniques for performance reasons. All are necessary for smooth, fast data flow.
-- Caching
Micropolis AV drives have an unusually large (512-KB) on-board cache for buffering data.
-- Error Correction
Many hard drives attempt to reread misread data, causing pauses of up to 850 ms. Micropolis AV drives couple a large cache with intelligent error-correcting firmware that attempts error correction on the fly.
It eliminates extra revolutions other drives use in the error-correction process. The company says hardware-based error correction will be incorporated in future versions of AV drives.
-- Thermal Calibration
All hard drive platters expand and contract with temperature changes depending on how heavily they're used and how much the ambient air temperatures vary. Thermal calibration (TCal) adjusts the read/write heads using servo information. Non-AV drives typically do this as a timed event, usually every 10 minutes or so. This can take up to 40 ms. Micropolis AV drives calibrate only one head at a time and never while a read or write is in progress. In addition, Micropolis AV TCal attempts to wait until the internal cache is full.
-- Rotational Speed
Micropolis AV drives spin at 5400 rpm, versus 3600 rpm for older hard drives. The faster the platters spin, the faster the data can be retrieved (although this requires sophisticated electronics).
-- Head Degaussing
The thin-film head
technology used in the AV drives (and used by other manufacturers in some drives) has a tendency to become randomly magnetized. This increases the signal-to-noise ratio of the data and requires extra error correction. Demagnetizing the heads requires writing to dedicated areas of the disk that aren't used for normal data storage. Non-AV drives put this area on the edge of the platters. Micropolis scatters these areas throughout the platters for minimum overhead.
No Interruptions, Please
