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CD-ROM ABCs
CD-ROM interfaces
CD-ROM transfer rates
Other CD technologies
CD-ROM error codes
Loading CD-ROM drivers
CD-ROM driver listing
CD definitions
CD-ROM troubleshooting

CD-ROM ABCs

A CD-ROM (Compact Disk Read Only Memory) is a drive that reads aluminum-coated round plastic discs but is incapable writing to any disc. Invented in the United States on 1972, the CD-ROM standard was officially introduced in 1982 when Philips and Sony agreed on the 4.72-inch size format we now use today. Later, as Phillips and Sony continued cooperation in the 1980s, additional specifications were announced concerning the use of CD technology for computer data which evolved into computer CD-ROM drives used today.

     The CD-ROM diskettes are 12 x 12 cm with a width of .1cm, as shown in the above picture. The disc is made of a polycarbonate wafer and is coated with a metallic film, usually an aluminum alloy. This aluminum film is the portion of the disc that the CD-ROM drive reads for information. The aluminum film (strata) is then covered by a plastic polycarbonate coating that protects the underlying data. A label will usually be placed on the top of the disc and data is read from the bottom of the CD.

CD-ROM INTERFACES

SCSI (Small Computer System Interface) - These require a SCSI Host adapter card connected into the system. These cards may be ISA, VLB or even PCI bus cards. It is highly recommended to get a card that matches the CD-ROM drive as some of the earlier drives had proprietary SCSI interfaces. Otherwise, a SCSI-2 card is recommended. See more information see SCSI page.

IDE (Integrated Device Electronics) - These CD-ROM drives connect to an IDE port on the motherboard or hard drive interface card. Usually, the IDE controller on the hard drive is set as master and the CD-ROM drive is set to slave. IDE is commonly used for CD-ROMs in standard computers today.

Panasonic - Very popular method of hooking CD-ROM drives to PC systems. The interface is usually part of a sound card. Creative Labs uses a Panasonic style (40-pin flat ribbon cable) for their Sound Blaster cards. The Panasonic interface does not require an IRQ but communicates directly through the port address.

Sony & Mitsumi - Other interfaces sometimes found in sound cards like the Sound Blaster MultiCD. The Mitsumi also uses a 40-pin flat ribbon cable while the Sony uses a 34-pin flat ribbon cable. These interfaces do require an IRQ.

Parallel - Parallel port CD-ROM drives come with special drivers to help communicate through a PC system's parallel port. The transfer rate tends to be slower than other interfacing methods. Biggest advantage is the portability between systems including notebooks.

PCMCIA (PC Card) - Interface now exists for connecting an external CD-ROM drive through the system's PCMCIA port. This is good for portability and provides faster access than the Parallel port would. For more information see PCMCIA page.

OTHER CD TECHNOLOGIES

CD-R - (CD Recordable) Drive which you are able to write to once. Once the drive is written to, it cannot be erased.
CD-RW - (CD ReWritable) drive which is a popular alternative to the CD-R drive. CD-RW has the capability of being written to at least one thousand times. The drawback with CD-RW discs is with the lower reflectivity of the disc itself can limit the readability. Many CD-ROM and CD-R drives may have a difficult time reading these disks.
DVD - (Digital Versatile Disc) New standard released in 1995 which originally was called Digital Video Disc and later changed to Digital Versatile Disc. DVD offers an initial storage capacity of 4.7GB (of digital information on a single-sided, single-layer disc the same diameter and thickness of a current CD-ROM
DVD-RAM - ReWritable drive type that uses a phase-change technology like the CD-RW drives. However, DVD-RAM discs cannot be read by standard DVD-ROM drives because of the differences in both reflectivity of the medium and the data format.