CD-ROM

CD-ROMShort for Compact Disc-Read Only Memory, a CD-ROM (shown right) is an optical disc which contains audio or software data whose memory is read only. A CD-ROM Drive or optical drive is the device used to read them. CD-ROM drives have speeds ranging from 1x all the way up to 72x, meaning it reads the CD roughly 72 times faster than the 1x version. As you would imagine, these drives are capable playing audio CDs and reading data CDs. Below is a picture of the front and back of a standard CD-ROM drive.

Computer CD-ROM drive

Opening and Closing a CD-ROM drive

CD-ROM eject buttonA CD-ROM drive can be opened by pressing the tray eject button on the front of the drive, as shown in the picture above and to the right. To close the CD-ROM drive, press the tray or the eject button again.

Tip: With some computer cases the eject button may be hidden behind the case to make the case look more visually appealing. If you see no button try pressing on the right side of the disc drive, which is typically toward the top of the tower.

You can also manually open or eject the CD-ROM drive by using a paperclip and inserting the end of the paperclip into the manual eject hole on the front of the drive. Insert it gently until you feel resistance, then press in a little further to activate the release mechanism. If done properly the tray should open a little bit and you can use your fingers to gently pull the tray out.

Interfaces

Below are the different interfaces that allow a CD-ROM and other disc drives to connect to a 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 (Mbit/s) Access time (ms)
Single speed (1x) 1.2288 400
Double speed (2x) 2.4576 300
Quad speed (4x) 4.9152 150
Six speed (6x) 7.0653 150
Eight speed (8x) 9.8304 100
Ten speed (10x) 12.288 100
Twelve speed (12x) 14.7456 100
Eighteen speed (18x) 21.8343 90
Twenty speed (20x) up to 24.576 90
Thirty-two speed (32x) up to 39.3216 85
Thirty-six speed (36x) up to 44.2368 80
Fifty-two speed (52x) up to 63.8976 80
Seventy-two speed (72x) up to 88.4736 75
CAV drives (12x - 24x) 1,843,200 - 3,686,400 150-90

Related pages

Also see: CD terms, Storage device