Chapter 10. CD-ROM Drives

CD-ROM drives are so standardized and ubiquitous that, excepting high-end SCSI models, they have become commoditized and are now obsolescent. Despite that, it's important to understand CD-ROM technology because it is the basis for current technologies including CD writers, DVD-ROM, and DVD writers.

If you use a CD-ROM drive only to play audio CDs, load software, and so on, nearly any recent CD-ROM drive suffices. If you need to replace a failed drive or buy a drive for a new PC, you can use an inexpensive ATAPI CD-ROM drive?while they remain available?or you can substitute an ATAPI DVD-ROM drive, which also reads CDs. If you put more demands on a drive, such as accessing databases, playing games directly from CD, or using the drive as a source to duplicate CDs, it's worth learning about the differences between currently available drives.

This chapter and the following chapter cover standard CD-ROM drives and CD writers, both of which store data on optical discs. Most drive manufacturers other than Seagate use the spelling "disk" for drives that use magnetic storage. By convention, all manufacturers use the spelling "disc" for drives that accept optical media.

Many people are careful about the clear side of optical discs but take less care with the label side. In fact, the clear side is a tough, protective polycarbonate layer. Data actually resides on a thin aluminum substrate immediately beneath the label. Because the label is very fragile, it is the label side that deserves careful handling.

Commercially produced discs record data as a series of microscopic pits and lands physically embossed on an aluminum substrate. Optical drives use a low-power laser to read data from those discs without physical contact between the head and the disc, which contributes to the high reliability and permanence of optical storage. Write-capable optical drives use higher-power lasers to record data on special discs. CD-Recordable (CD-R) records data permanently to the disc, and is also called Write-Once. CD-Rewritable (CD-RW) allows data that has been written to be erased or overwritten, and is also called Write-Many.