 Number 206 - July 2000 |
| CD Drive Can Only Talk in Its Native Language | ||
| from Q & A by Patrick Marshall Seattle Times, Apr 23, 2000 | ||
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Q. We have a
Gateway P120 with a 6X CD-ROM drive. Our son made a CD-ROM disc from his
computer for my husband to use. When we put it in the drive, absolutely
nothing happens and the system doesn't recognize there is a disc in the
drive. When we put it in our new computer, a Gateway 450, it works just
fine. It also works on our son's computer. What do you think could be
the problem? Commercial CDs work just fine.
-Jill Eshenbaugh jeshenba@telebyte.net A. It may seem like CDs and CD drives are all alike but they are not. Commercial CDs have a metallic reflective layer that is placed directly against the clear base of the disc. This metallic layer has been molded with pits during manufacturing to contain the data. When the CD is played, the CD drive employs a light to "read" the pits. When the beam hits a flat area, the light is reflected directly back. When the beam hits a pit, it is diffused. The drive reads these differences in |
reflectivity as data. CD-R discs, on the
other hand,
require an extra layer of light-sensitive dye to record the data. When
the disc is exposed to the recording laser beam, it changes color and
reflectivity. That's why you can clearly see a darker band on CD-R discs
where data has been recorded. Anyway, with CD-R discs, the light beam
reflects off the changed spots in the light-sensitive dye. Rewritable
discs (CD-RW) employ yet another technology for recording data involving
compounds that can be "melted" by the laser beam so that they can be
rerecorded with data. The long and the short of it is that some CD
drives--and especially older ones--may not be good at reading CD-R or
CD-RW discs while they may do a perfectly fine job of reading commercial
CDs.
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Number 206 - July 2000
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