CD-ROM

Short for Compact Disc-Read Only Memory, CD-ROM drives or optical drives are CD players inside computers that can have speeds in the range from 1x and beyond, and have the capability of playing audio CDs and computer data CDs. Below is a picture of the front and back of a standard CD-ROM drive.

Interfaces

Below are the different interfaces that allow a CD-ROM and other disc drives to connect to the computer.

• IDE/ATA - One of the most commonly used interfaces for disc drives.
• Panasonic - Older proprietary interface.
• Parallel - Interface used with old external CD-ROM drives.
• PCMCIA (PC Card) - Interface sometimes used to connect external disc drives to laptop computers.
• SATA - Replacing IDE as the new standard to connect disc drives.
• SCSI - Another common interface used with disk and disc drives.
• USB - Interface most commonly used to connect external disc drives.

CD-ROM transfer speeds

Below is the standard transfer rates and access times for CD-ROM drives. The below figures are averages you can expect to find on each speed of CD-ROM drive.

Drive speed	Transfer rate (BPS)	Access time (ms)
Single-speed (1x)	153,600	400
Double-speed (2x)	307,200	300
Triple-speed (3x)	460,800	200
Quad-speed (4x)	614,400	150
Six-speed (6x)	921,600	150
Eight-speed (8x)	1,228,800	100
Ten speed (10x)	1,536,000	100
Twelve speed (12x)	1,843,200	100
Sixteen speed (16x)	2,457,600	90
Eighteen speed (18x)	2,764,800	90
Twenty four speed (24x)	3,686,400	90
Thirty two speed (32x)	4,915,200	85
One hundred speed (100x)	15,360,000	80
CAV drives (12x - 24x)	1,843,200 - 3,686,400	150-90

• Further information about the trailing x on a CD-ROM can be found on our x definition.

Also see: CD definitions, Storage