Sony CRX100E User Guide - Page 5

CD-RW discs can be written to many times. CD-RW media is rated for one thousand different writes to the media. CD-RW is a perfect medium for creating reliable backups that can be added to as necessary, and even rewritten as your backup scheme requires. While CD-RW media is more expensive than CD-R media it has a lower cost per megabyte than other competing technologies, such as MagnetoÐOptical or even magnetic removable media drives. CD-RW drives are very versatile for transporting information to both older and newer CD and DVD ROM drives. CD-RW media can be read by newer CD-ROM and DVD drives. These newer drives are known as Multi-Read (MR) drives. And even though CD-RW media cannot be read by older CD ROM drives, the Spressa USB can write to CD-R media which can be read by standard CD-ROM drives and CD Players. How CD-R and CD-RW work CD-ROM drives (CD-R and CD-RW drives as well) read the one and zero bits by difference in reflectivity. Mass produced Compact Discs are created by stamping ÒpitsÓ in the CD. These ÒpitsÓ reflect differently than the ÒlandÓ which is the area between Òpits.Ó CD-R drives work by using a laser beam to heat the recording layer, causing a chemical reaction in that spot so CD-ROM players will see this as a ÒpitÓ and the unburnt area as Òland.Ó CD-RW uses what is known as a ÒPhase ChangeÓ technology. In the CD-RW media is a substance which can be changed from an amorphous ÒmarkÓ that very closely resembles the pits of a stamped CD, to a crystalline state which resembles Òland.Ó The laser beam of the Spressa USB changes the crystalline state to the amorphous state by use 2 CRX100E/X - Spressa USB User's Guide of a laser to quickly heat the spot on the disc, forming a mark. To change the amorphous state back to the crystalline state the laser beam uses a lower power setting to transition the mark back to the crystalline Òland.Ó Performance Because of the different processes involved, the Spressa USB performs at different speeds for writing CD-R and CD-RW discs. The Spressa USB is capable of writing CD-R media at quad speed (4X) and CD-RW discs at double speed (2X). Double speed means that the Spressa USB is capable of writing CD-RW media at 300 kilobytes per second (kb/s). This rate allows the Spressa USB to record a full 650 megabyte CD-R or CD-RW disc in about 36 minutes. Quad speed means that the Spressa USB can write (also called record or burn) CD-R media at 600 kilobytes per second. This rate allows the Spressa USB to record a full 650 megabyte CD-R disc in about 18 minutes. The Spressa USB is a multi-function device, capable of reading at 6X Maximum (900 kilobytes per second). The speed at which a CD ROM is written does not affect the speed at which that CD ROM can be read. For example, a CD ROM which was written at 2X can be read at 1X, 2X, 4X, 8X, 12X, 24X and so on. Buffer The Spressa USB has a one megabyte data buffer, which protects against buffer underruns when writing to CD-R media. Buffer underrun is a condition where the driveÕs buffer runs out of data while the CD-R or CD-RW media is still being written. The recording of a CD is a system intensive process, and the recorder needs a constant stream of data. A buffer underrun occurs when the data stream to the recorder is not fast enough to keep the recorderÕs buffer full, causing the recording to abort. CRX100E/X - Spressa USB User's Guide 3