Academic journal article Library Technology Reports

CD-ROM Drives: An Overview

Academic journal article Library Technology Reports

CD-ROM Drives: An Overview

Article excerpt


As recently as six years ago, the CD-ROM industry was embroiled in a classic "chicken and egg" debate. Database makers argued that they could not fully develop CD-ROM products because there were no drives on which to run them. Drive manufacturers, on the other hand, argued that they were concentrating on a guaranteed but narrow market base for CD-audio equipment since database companies couldn't sort out just which were the "best" products to take advantage of the incredible potential of CD-ROM hardware.

If you can remember the early days of television, the situation was pretty much the same. There was not enough programming to justify the purchase of an expensive TV by most people, and that discouraged the mass manufacturing of equipment that would result in an affordable product.

Well, as with the growth of television, the growth of the CD ROM industry was only a matter of time. Today the more than 3,500 databases in the United States have created a sufficient drive market to attract even the most cautious of hardware vendors.

The first CD-ROM drives, produced by only three manufacturer all had pretty much the same features, making shopping easy. Now, drive from a variety of manufacturers offer a number of different features and wide array of performance characteristics. The most important features involve the form factor (internal or external), the type of adapter or interface, the data access and transfer speeds, the size of the buffer, reliability, and bundling options.


A CD-ROM drive can go inside or outside the computer case. Internal drives tend to be less expensive because they don't require a protective case. Since they require an internal bay, they are more suitable for a standalone system or for use in a separate multi-drive tower. An external drive permits chaining together as many as seven or eight drives, making it easier to mix and match drive brands or to swap them between several computers.

Space often becomes a prime consideration. Internal half-height drives take up only half the vertical space of their full-height counterparts, leaving more room for other devices like floppy drives or tape backup units. While external drives are often classified as half-height or full-height, the overall dimensions (height, width, and depth) give a better indication of how much desk space they require.


All drives require a host adapter or controller card to connect to the computer and govern operation. Here, you have two choices: a proprietary or a SCSI (Small Computer Systems Interface) card. A proprietary interface can only support the drive it comes with, or some of the drives made by the same manufacturer. Most manufacturers now offer drives that use a SCSI connector. Some even use a SCSI-2 interface, which is backwardly compatible with the SCSI command set.

A Macintosh computer comes with a built-in SCSI interface, unlike the PC. Consequently, a SCSI model allows sharing a CD-ROM drive with a Macintosh. You can also use a SCSI interface to attach the CD-ROM drive to a notebook computer via a MINISCSI parallel to SCSI converter. Some local area networks, like SCSI Express, also require a SCSI interface. A SCSI interface also allows users to chain up to seven devices to the same card. Generally, one would chain together several CD-ROM drives; however, the SCSI interface should also support dissimilar devices like a scanner, an external hard disk, or other SCSI devices. SCSI interfaces tend to be a little more expensive than proprietary ones.

The interface card determines which computers will support particular CD-ROM drives. SCSI drives, while a little more expensive, generally allow for more flexibility.


The average data access time indicates the average time it takes the CD-ROM drive to locate the desired information. …

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