CD/DVD Drive Overview

Compact Disc (CD) and Digital Versatile Disc (DVD, formerly Digital Video Disc) drives are called optical drives because microscopic pits embedded into the discs are read by measuring reflected laser light. Read-Only Memory (CD-ROM) drives became popular around 1994 and represented a major improvement over floppies for program installation. They can also be used to read from CD data discs. Eventually came CD-R drives, which allowed discs to be burned (recorded) once only. There weren't too many of these made as they were quickly replaced by CD-RWs, which can be used with both single-use and rewritable discs. DVD-ROM drives were next. These are used to play DVD videos and read from data DVDs. More and more programs are becoming available on DVDs as well.

Note The term ATAPI refers to IDE optical drives.

Unfortunately, there are several different incompatible types of DVD writable drives available, and the industry has not settled on a standard. The different types include the following:

DVD-R: Can write to a blank disc once. The discs are compatible with most recent DVD video players.

DVD-RW: Can be written and rewritten to. The discs are compatible with most recent DVD video players.

DVD+RW: Can be written and rewritten to. They can read and write to DVD-Rs. The discs are compatible with some DVD video players.

DVD-RAM: Can be written and rewritten to. The discs are not compatible with most DVD video players as of this writing.

Blu-ray Disc: A format not yet available as of this writing that allows for up to 27GB of data to be stored on a single DVD disc.

Some multi-standard drives are available. There are also discs with multiple layers and discs that can be flipped over to record on the other side, increasing the data capacity. Stay tuned; the industry will probably eventually come to an agreement on a single standard.

Selecting Optical Drives

There are only a few considerations in selecting an optical drive.

Interface

So far, internal drives come only in two interfaces: IDE and SCSI. IDE is the same interface as EIDE as it applies to hard drives, and thus the optical drives are connected to the same cables as the hard drives. See tutorial 6, "Magnetic Disk Drives," for more information on the IDE interfaces. SCSI drives are simply additional devices in the SCSI chain. SCSI controllers and consequently, SCSI drives, are found almost exclusively in heavy-duty business computers. Serial ATA optical drives will be available eventually.

External drives once came with parallel interfaces (they connect to a parallel port on the computer) and SCSI, but now are available in USB and FireWire. You should select the fastest interface the user can afford. Also note that USB 2.0 is faster than the USB 1.1, so if you are using a USB 2.0 drive with a computer that has only a USB 1.1 interface, the drive will operate at the slower speed.

Speed

Speed of optical drives is based on the data transfer rate of the original CD-ROM drives, 150 kilobits per second (Kbps). For example, the data transfer rate of a 52x CD-ROM drive is 52 × 150, or 7.8 megabits per second (Mbps). Even the fastest optical drives, however, are slower than hard drives.

CD-RW Speed

A CD-RW, also known as a CD burner, has three speeds listed in its specifications. The first number represents the speed of writing to a CD-R, the second is the speed of writing to a CD-RW, and the third is the speed it reads a disc. In the case of a combo drive that offers a DVD-ROM along with a CD burner, a fourth number is the speed the drive reads a DVD, but see the next item for an explanation of DVD speeds.

DVD Speed

There are combo drives available that offer DVD and CD burning capabilities. In these cases, there are so many numbers in the specifications that each is spelled out (or should be) wherever it is displayed. The single DVD-burning speed, however, is much faster than the CD's 150 Kbps, and can vary from standard to standard. The actual speed in Mbps should be spelled out in the documentation.

Note The maximum speed of the blank media (writable discs) in any format must match or exceed that of the burner in order for the burner to operate at its maximum rated speed.

Backups onto Optical Discs

Microsoft Backup, which comes with Windows except for XP Home Edition (Start > Programs/All Programs > Accessories > System Tools > Backup), can use optical drives. Many third-party backup programs have this capability as well. Elect to back up to a file and then store the file, if it will fit, on a CD-RW or writable DVD. You can use software to burn a disc, or better yet, format a rewritable disc so that it can be used just as a magnetic drive. Most or all CD-burning software has a function for formatting the disc. To format a disc could take between 25 and 45 minutes. When it is completed, files and folders can be dragged and dropped, or cut/copied and pasted into and out of the rewritable disc. This makes these discs very convenient to use for backups. Keep in mind that formatting a rewritable optical disc will preclude its use in a DVD or CD video/music player.