Derived from the 2-1/2-inch MD (Mini Disc) technology that Sony introduced in 1993 for the consumer music and broadcast markets,
Sony's MHD-10 MD Data drive
is another contender in the ever-evolving removable media market. MD drives use MO (magneto-optical) technology with a proprietary compression scheme. The original consumer version stores 74 minutes of CD-quality audio; the computer-peripheral version stores 140 MB of data on the 2-1/2-inch media.
Unlike typical MO drives, MD drives don't use laser modulation and a two-pass erase-to-zeros/write-the-ones process to write data. Because MD drives spin much slower than MO drives, they can use magnetic modulation to write data. In an efficient, single-pass process, the MD drive's laser heats each magnetic bit to its Curie temperature (365F) while a magnetic head on the other side of the disc writes th
e data pattern.
The MD Data drive stands alone among removable media drives in offering different flavors of discs. Besides the standard read/write discs, read-only discs are designed for software distribution or CD-ROM-like applications. Furthermore, Sony also offers hybrid discs with both read-only and read/write sections. Designed primarily for applications such as interactive games, these discs let players save scores and character profiles. Sony MD Data drives can also play the Audio MiniDiscs found in larger music stores.
Announced in early 1994, the MD Data drive has suffered numerous delays, but Sony expects volume shipments by the time you read this. The delays have hurt Sony's attempts to forge alliances with hardware and software companies to make MD Data a new industry standard. Competitors (especially Iomega) have been able to get a leg up on the market by offering drives with lower prices and higher performance. MD Data drives have an access time of 500 ms and a data transfer rate
of only 150 KBps, which places their performance closer to that of floppy drives than to that of hard drives.
Initially available only as an external SCSI unit, the drive is powered by batteries or an AC adapter. The $749.99 list price makes the MD Data drive a rather pricey alternative to the Iomega Zip and SyQuest EZ135 lines. While the Sony MD Data drives are certainly a unique and interesting technology, they may be too little, too late, and much too expensive.
Sony's MHD-10 MD Data Drive
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Sony's Mini-MO
