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You might think of erasable magneto-optical (MO) disc drives as extremely fast, capacious floppy disk drives.
You could easily mistake a 3-1/2-inch MO cartridge for a 3-1/2-inch floppy disk. Width and length are identical; there's the same write-protect tab and sliding metal cover, and the same hard plastic shell that lets you carry the disk around in a shirt pocket without harming it.
But slide open the metal cover of a cartridge and you'll see the rainbow sheen of an optical disc. This disc can read and write a whopping 128 megabytes at speeds close to those of a hard drive. The 5-1/4-inch MO discs are slower, but they also hold more data--up to 650 megabytes--on one double-sided disc.
In this product comparison we look at four 3-1/2-inch magneto-optical disc drives and two 5-1/4-inch drives, representing four manufacturers. They include two 3-1/2-inch drives from Pinnacle--one a Magneto Optical Storage Technology (MOST) mechanism that's been shipping for almost a year, and the other a new Sony-based drive. (According to Pinnacle, it will continue to sell the older MOST drive.)
You can purchase each of the drives as complete subsystems, consisting of an external drive, interface kit (SCSI controller, software and cables), and the removable optical disc.
The 5-1/4-inch MO drives have been around since 1988, so they have a much larger installed base of customers than the 3-1/2-inch drives. The latter are just beginning to hit the market en masse; several vendors missed this comparison's deadline by only a couple of weeks.
ALLURE OF THE MAGNETO. Magneto-optical discs make ideal secondary storage devices, but they are not quite fast enough to replace fixed hard drives in every application. Average access time for 3-1/2-inch drives is in the 30-to 60-millisecond range, compared to 10 to 20 milliseconds for hard drives. The 5-1/4-inch drives are slower, with access times in the 60-to 100-millisecond range. This usually means it will take two or three times longer to find a file on a 3-1/2-inch magneto-optical drive than on your hard drive. Conversely, 3 1/2-inch magneto-optical drives are three times faster than a floppy's average 180-to 200-millisecond access time.
The initial cost of buying a magneto-optical drive is much higher than that of a hard drive of equal storage capacity....