At the spring COMDEX conference in Atlanta, a group of ten major computer hardware and media manufacturers announced their intention to develop a new CD-Erasable (CD-E) format based on Phase Change technology.

Philips Leads Proposal for Development of CD-Erasable

Hugh Bennett
CD-ROM Professional, July 1995

At the spring COMDEX conference in Atlanta, a group of ten major computer hardware and media manufacturers announced their intention to develop a new CD-Erasable (CD-E) format based on Phase Change technology. The proposal for the fully-rewritable CD system, put forward by Philips Electronics NV, is being supported by Hewlett-Packard, IBM, Ricoh, Sony, 3M, Olympus, Mitsubishi Chemical Co. (MCC), Matsushita Kotobuki Electric Industries (MKE), and Mitsumi Electric Co. A more formal industry announcement came later at the Optical Storage Technology Association (OSTA) meeting in May.

The proposal calls for the manufacture of multifunction devices incorporating the capabilities of a CD recorder and CD-E and CD-ROM drives. Such units would be able to read and write CD-Recordable (CD-R) discs, read standard CD-ROMs and write, read, and re-write the new CD-E discs. These CD-E discs will not be backward-compatible with existing CD-ROM drives, but new CD-ROM drives coming to market will be able to read CD-E discs with only “minor” modifications to their automatic gain control, allowing the units to vary their laser power and compensate for the lower reflectivity of the discs. CD-E media reflectivity is expected to be between 15 and 20 percent in comparison to CD-DA/CD-ROM’s minimum of 70 percent (Red Book) and CD-R’s minimum of 65 percent (Orange Book).

HOW CD-E WORKS
In its initial form, Phase Change CD-E media is in an amorphous state. To write data, high energy laser light is focused on the amorphous material and spots exposed to the light change into a crystalline state. To read data, a low-intensity laser beam is applied to the disc and is either reflected off these crystalline spots or scattered by the amorphous background mimicking the pits and lands of a standard CD-ROM. A photo detector then registers the differences in reflectivity and translates the binary differences back into the original data. The disc can be directly overwritten by focusing even higher energy laser light on the crystalline structures and melting them back into their original amorphous state in a process of revitrification.

POSSIBLE PRODUCT DELAYS
CD-E is currently in the feasibility stage so Philips’ proposal is really an expression of the state-of-the-art in compact disc research rather than a product introduction. Before product development takes place, various working groups within OSTA will have to examine the implications of implementing CD-E such as alterations in logical structures (like ISO 9660 or ECMA 168) to accommodate dynamic file changes or modify driver level software (like MSCDEX or CDFS) to read a new file system.

Still, the companies involved hope to issue a technical draft in the third quarter of 1995 and ship CD-E drives in the first half of 1996. Few analysts doubt that the technology is ready, but if changes are required to existing ISO standards or new standards must be approved, they fear CD-E may be bogged down in committee and delayed. Then again, given Microsoft’s operating systems dominance, and if driver changes prove to be necessary, CD-E’s timing and success may ultimately depend upon Microsoft’s willingness to adapt MSCDEX or CDFS.

WILL IT REPLACE CD-R?
Philips and a number of industry observers see CD-E as a logical extension and complement to CD-R, rather than as a replacement or competing system and expect that the two technologies will co-exist for a number of reasons. A central one is CD-R’s backward compatibility with the already huge installed base of audio, CD-ROM, CD-i, Video CD, and dedicated game drives and players. Another key reason is the price of blank media. Phase Change discs are physically more complex than CD-R discs and are manufactured in a radically different way. Blank CD-R media will always be significantly less expensive than CD-E media and have a lower cost per megabyte of storage. Phase Change discs also have vastly different characteristics than CD-R discs such as rewritability and data life. It is generally accepted that traditional Phase Change media has an expected life of approximately 30 years whereas CD-R media is projected to be more than 100 years.

In comparison to other rewritable solutions like Magneto-Optical (MO), Phase Change media traditionally suffers from limited cyclability, or a limited number of times which data can be rewritten to a disc before a failure of the recording surface. Great strides have recently been made in this area, but CD-E’s cyclability will ultimately depend upon cost and manufacturing tradeoffs affecting the final choice of material used in the recording layer. Despite the direct overwrite capabilities of Phase Change, CD-E will also have significantly less performance than MO because of the reliance on a Constant Linear Velocity (CLV) rotational scheme instead of a Constant Angular Velocity (CAV) or Zoned Constant Angular Velocity (ZCAV) system.

POTENTIAL USES FOR CD-E
These fundamental differences mean CD-R will remain a good choice for low cost data distribution, prototyping and secure archiving while CD-E and MO will be more desirable for online storage, quick and uncomplicated backup and temporary data transport. New markets like HSM (Hierarchical Storage Management) might also employ CD-E, but the holy grail remains a replacement for the floppy disk. Some analysts think a reasonably priced drive that reads standard CD-ROMs and rewrites 650MB CD-E discs might just be what the market has been waiting for, although strong competition will come from Iomega’s Zip, Syquest’s EZ135 and new higher capacity and smaller sized MO formats.

About the Author

Hugh Bennett, editor-in-chief of Hugh’s News, is president of Forget Me Not Information Systems, a reseller, systems integrator and industry consultant based in London, Ontario, Canada. Hugh is author of The Authoritative Blu-ray Disc (BD) FAQ and The Authoritative HD DVD FAQ, available on Hugh’s News, as well as Understanding Recordable & Rewritable DVD and Understanding CD-R & CD-RW, published by the Optical Storage Technology Association (OSTA).

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