DD-RW: Double Density Read-Write (CD). A rewritable CD format introduced in April 2001 by Sony. DD-RW uses ISO 9660 format but shrinks the intertrack spacing from 1.6 to 1.1 microns and the minimum pit length from 0.833 to 0.623 micron. The format is identified as "purple book". This allows them to put 1.3GB on a standard sized CD. DD-RW drives will read and write ordinary CD/CDR/CDRW disks. The drive rotation speed is reduced in DD mode.

The drive and media cost more than ordinary media and hold more data. They cost less than rewritable DVD and hold less.

Sony's initial drive is ATAPI compatible. It has 8MB of on drive data buffering. Claimed speeds are Read 32X, Write 12X, Rewrite 8X. Drivers are apparently available only for Windows.

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