CD-ROM#CD-ROM drives

A CD -ROM drive (also called CD-ROM drive ) is an apparatus for reading CDs and CD-ROMs in particular. The disc is rotated at a speed between 200 and 10000/min and is sampled by a low power laser (class 1), which moves radially on a carriage. This is achieved at each point on the CD is free access. The first CD -ROM drives came in 1985 on the market. In the meantime ( as of 2011) they have been almost entirely supplanted by DVD drives or CD / DVD combo drives.

  • 2.1 Interface to controller
  • 2.2 Audio outputs
  • 5.1 CD burner
  • 5.2 DVD drives
  • 5.3 DVD successor

Designs

Format

There are two standard versions: 5.25 " ( eg, PCs ) and 3.5 " SlimLine (eg for laptops ).

Inserting the optical medium

There are various methods such as optical disc into the drive and then can go out.

  • Drawer drives have a drawer that can be a extended and retracted via a button on the front of the drive or software controlled. The optical storage medium is inserted into the drawer. Nowadays, this is the most common type. The first types were suitable only for horizontal installation. Later drives appeared with brackets that allow the optical medium could also be inserted into a vertically built-in drive, without falling out. Example: Toshiba SD- L902A.
  • Slot-In drives have only a narrow slot in the optical medium is inserted. The ejection is also done at a keystroke or via software. By eliminating the drawer there are fewer mechanical parts that could wear out eventually. Example: Panasonic CW - 8124B
  • In caddy drives the optical medium is placed in a special envelope, the caddy. Then the caddy is inserted into the drive. Advantage of this technique: Each disc can remain in their own caddy, where it is protected from damage and contamination. Disadvantage, the caddies cost extra money. This technique is no longer in use today. Example: Plextor 4Plex.
  • Top - loaders are drives that have a flap on the top. For inserting and removing the lid is opened. This variant is not suitable for internal drives. Today it is used sporadically yet for externally connected drives. Plextor PX- 608CU.
  • However, there was a special form, which was also suitable for installation: The combination of top - drawer loader and drive. Here, the drive itself forms ( with the exception of a holding frame and the rear connections ) the drawer. By applying pressure to the front drive travels from the drive. Then a door can be opened. This drive shape is no longer manufactured today. Example: Mitsumi LU005S.
  • In CD-/DVD-Wechslern can be several CDs / DVDs accommodate, so a change, especially in media commonly used, is eliminated. Drives of this type lend themselves to especially if several CDs / DVDs should be made in a local network or via the Internet. In this age of terabyte hard drives such changers have lost in importance, as can be CDs and DVDs in large numbers on playing on hard drives. The reading speed of hard drives is also significantly greater than that of CD and DVD drives, in addition accounts for the change process. Example: Pioneer DRM - 6324X

CD-ROM reading unit

Movable carriage for random access to the CD

Emergency

With drawers, slot-in drives and caddy drives can be found on the front usually a so-called Emergency. This allows the ejection of the disk, even if the drive has no power (eg when the computer is off ). There is a 1-2 mm wide, round opening in which a long, thin object, usually a straightened paper clip, can be introduced. By pressing on the hidden mechanism behind the drawer, CD / DVD caddy or be ejected.

Interfaces

Controller interface

The most commonly used interface is ATA. There are also SCSI and SATA for internal drives as well as USB and Firewire external drives. Some of the first CD -ROM drives (Sony, Panasonic, Mitsumi ) have proprietary interfaces for the appropriate controller card ( legacy ISA cards) are available. Also, some sound cards ( legacy ISA cards) this time have appropriate connections. In addition, legacy ISA cards that provide a single ATA interface, as "CD - ROM controller " sold.

Sound card with connectors for proprietary CD -ROM drives: Sony ( SONY ) Mitsumi (MIT), Panasonic ( PAN)

IDE CD -ROM drive,

Audio outputs

CD -ROM drives generally have an analog and a digital audio output.

The pins for the analog output are specified as follows:

Nose Right Ground Ground Links if you look at the pins.

For drives in the 5.25 "format located at the front of the addition is usually a line-out output (usually in combination with a volume control ) to which, for example, a headset can be connected.

Power supply

Internal CD -ROM drives have a 4-pin Molex connector for the power supply. External drives have either a built-in power supply, a connection for an external power supply or be supplied with power via USB, if the drive does not require more than 500 mA of current. Depends on the drive to a hub with other devices, this can be a problem because the drive must then divide the 500 mA with other devices, unless the hub has its own power supply.

Speed

With the first CD-ROM drives (as of 1985 ), the data were at a rate of 150 KB / s read ( simple speed 1x). At this reading speed occurs because the music information is stored on the earlier developed Audio CD in 16 -bit stereo and 44.1 kHz, which is a stream of 44.1 kHz x 16 bit x 2 channels (because stereo ) = 176.4 KB / s gross yields and 150 KB / s net (without error correction). Soon, the speed was gradually increased ( in the mid-90s there were terms like double-speed or quad -speed drive for drives with two or four times the speed ), with up to 60 times speed 100 revolutions per second and thus a limit is reached beyond which there is a risk that the disc is damaged by the centrifugal forces acting on them.

To increase the read performance drives have been developed, whose lasers to read multiple tracks simultaneously ( multi-beam ). When TrueX technique used by Kenwood the drive is reading seven tracks simultaneously. Such a device with virtually 72 times the reading speed can the CD with a maximum 2.700/min rotate and thus operates much quieter than a 52 -fold drive without Multibeam. However, it was never able to enforce due to the high purchase price. Drives, read only one track, usually have 3 beams, because they require more information for tracking in addition to the data stream.

See also: Spin Down

Developments

CD burner

To describe ( colloquially "burning" ) of CD -R and CD -RW have been developed with more powerful lasers specific drives. Since these devices to store the data locally melt the material, they are called CD burner.

DVD drives

The development of CD -ROM drives are the DVD drives and DVD burners that can read and write CDs and DVDs out. Since all these drives are based on the reading of the data by a laser, also referred to as a summary of optical drives.

DVD successor

Meanwhile, there are already the successor to the DVD at a multiple of storage capacity. These include Blu- ray Disc, HD DVD, VMD and HVD.

  • Storage drive
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