CD-ROM Storage
CD-ROM stands for Compact Disk - Read Only Memory. The actual CD-ROM disk looks similar to this:

CDs are the actual Compact Disks that you place in the CD-ROM drive. CDs hold approximately 650 MB of information.

However, you must have a "CD-ROM" drive to be able to see or use the contents of a CD. You will need a "recordable" CD-ROM drive if you want to record on a CD.

A compact disk (CD) is a plastic disk, coated with aluminum alloy. The "plastic" base is made of a poly carbonate wafer (if you want to know more, consult a chemical engineer). The CD is written to by a laser, and read by a laser. CDs are available in 63 and 74 minute versions.

Size - They are normally 4.72 inches (120 mm) in diameter, 1.2mm thick, and has a 15mm hole in the center for mounting in the drive. CD-ROM drives are rated in terms speed. The are single, 2, 4, 6, 8, 12, 16, 24, 36, 40, 48, 50, and even a 72 speed as of April 2000.

A single speed CD-ROM drive was designed to transfer data at 150 KiloBytes Ps (KBPS) per second. Each speed rating is a number times 150 kbps. So, a 2 speed should transfer data at a 300 KBPS, and a 10 speed should be 150 MBPS x 10 = 1,500 kbps. or about 1.5MBPS.

Access Time is another matter - typically 100 to 200 Milliseconds! Very slow, but the higher speed drives help overcome this through higher transfer rates.

CD-ROM interfaces are SCSI/ASPI (Advanced SCISI Programming Interface) and IDE/ATAPI (AT Attachment Packet Interface), and proprietary versions.

CD-ROM drives can be purchased in read-only versions, or in "write capable" versions. The cost is obviously different, but not unreasonable for a "write" capable drive.

"Recordable" versions of CD-ROM drives costs in April 2000 vary between $120-299.00 (different manufacturers and models) for an internal and external drives.

The CD's themselves are very inexpensive ($1.00 to $2.00 for write once CDs) and ($7.00 to $18.00 for re-writable CDs).

Future purchases of CD-ROM drives should be for drives with speeds of 48x or higher which are obtainable for around $68.00 or less.

Manufacturers:

  1. RICOH
  2. Hewlett-Packard
  3. Phillips
  4. Pennacle Micro