Compact Disc Read-Only Memory

storage (CD-ROM) A non-volatile optical data storage

medium using the same physical format as audio compactdiscs, readable by a computer with a CD-ROM drive.

CD-ROM is popular for distribution of large databases,

software and especially multimedia applications. The

maximum capacity is about 600 megabytes. A CD can store

around 640 megabytes of data - about 12 billion bytes per

pound weight.

CD-ROM drives are rated with a speed factor relative to music

CDs (1x or 1-speed which gives a data transfer rate of 150

kilobytes per second). 12x drives were common in April

1997. Above 12x speed, there are problems with vibration and

heat. Constant angular velocity (CAV) drives give speeds up

to 20x but due to the nature of CAV the actual throughput

increase over 12x is less than 20/12.

20x was thought to be the maximum speed due to mechanical

constraints but on 1998-02-24, Samsung Electronics

introduced the SCR-3230, a 32x CD-ROM drive which uses a ball

bearing system to balance the spinning CD-ROM in the drive to

reduce noise.

CD-ROM drives may connect to an IDE interface, a SCSI

interface or a propritary interface, of which there are three

- Sony, Panasonic, and Mitsumi. Most CD-ROM drives can also

play audio CDs.

There are several formats used for CD-ROM data, including

Green Book CD-ROM, White Book CD-ROM and Yellow BookCD-ROM. ISO 9660 defines a standard file system.

See also Compact Disc Recordable, Digital Versatile Disc.

Byte, February 1997.

(1998-03-16)