DVD-ROM and CD-R: the compatibility question answered

Emedia Professional, March, 1998 by Hugh Bennett

Sony also has the honor of being the first hardware company to ship a CD-R-compatible DVD-ROM drive. As well as reading CD-R and other compact disc formats using Sony's "Dual Discrete Optical Pickup," the company's DDU-100E is a single-speed DVD-ROM drive that offers eight-speed CD-ROM drive performance, an ATAPI interface, and tray-loading design.

In addition to its pioneering efforts on the DVD-ROM front, Sony is the only manufacturer currently offering DVD-Video players that are capable of reading CD-R discs. Introduced in April 1997 as a high-end DVD reference player, the $1,000 DVP-S7000 incorporates Sony's "Dual Discrete Optical Pickup" for playing both CD-R and pressed CD-Audio and Video CDs. With hardware prices continuing to fall, it is encouraging to note that Sony has retained the dual-laser pickup for its more consumer-oriented DVD player, the $599 DVP-S3000, which was introduced in October 1997.

Samsung Electronics: Two Lasers, One Lens

The second company to develop a CD-R-compatible DVD optical pickup was Korean giant Samsung Electronics, which announced its achievement in December 1996. Proving again that there are many ways of approaching and solving technical problems, Samsung's solution exemplifies a direction many other manufacturers have taken in their own product designs.

Unlike Sony's solution, which employs discrete CD and DVD optical systems and light paths, Samsung's pickup uses a single shared objective lens for both CD and DVD wavelengths. Equipped with 780nm and 650nm laser diodes, the pickup uses a largely shared light path and an annular masked objective lens to compensate for the different substrate thicknesses and to provide the correct numerical aperture for reading both families of discs.

The first commercial fruit of Samsung's efforts is the SDR-130 DVD-ROM drive, which includes CD-R read capability, 1X constant linear velocity (CLV) DVD-ROM reading, and 8X CLV speed when functioning as a CD-ROM drive. Samsung also continues the use of its innovative pickup in the drive's successor, the SDR-230 DVD-ROM drive, which was announced at COMDEX in November 1997. Like most second-generation DVD-ROM drives, the SDR-230 is fully CD-R compatible and boasts 2X CLV DVD-ROM and 20X constant angular velocity (CAV) CD-ROM performance.

Toshiba Corporation: R/ROM/RAM, READ/READ/REWRITE

Although Toshiba Corporation's initial DVD-ROM offerings could not read CD-R discs, CD-R has now been fully embraced in the second generation of products, which include not only DVD-ROM, but the initial DVD-RAM drives expected to ship sometime in early 1998 as well. Toshiba's SD-M1102 for desktop PCs offers 2X max CAV DVD and 24X max CD-ROM drive performance; the SD-C2002 17mm slimline model also brings DVD and CD-R compatibility to notebook computers with 2X max CAV DVD and 16X max CD-ROM speeds.

Since DVD-RAM proponents like Toshiba intend for rewritable DVD drives to replace read-only DVD hardware, rather than coexist in a separate bay in the computer, Toshiba's recently announced--but still-unshipped at press time--DVD-RAM drive meets the same stringent demands placed upon DVD-ROM drives to read most disc formats. In addition to rewriting 2.6GB/ side cartridged DVD-RAM discs, Toshiba's SD-W1001 SCSI and SD-W1002 ATAPI DVD-RAM drives read all DVD and CD formats.