MultiRead revisited: why Windows can't read

Emedia Professional, April, 1998 by Dana J. Parker

CD-ReWritable is well and truly launched, and doing quite nicely, thank you. The MultiRead CD-ROM drives required to read CD-RW media are steadily infiltrating the installed base, at an estimated rate of 60 million drives a year. Not one but two available programs (Adaptec's Direct CD 2.0 and CeQuadrat's PacketCD 2.0) will allow random erasability of CD-RW media in UDF format. In what might be some kind of industry record for the shortest proposal-to-product interval, recorder manufacturers, drive manufacturers, software vendors, and specification writers have succeeded in pulling together to make CD-RW happen. It seems that everything should be in place for the ultimate achievement of CD technology--all the functionality of the mythical 650MB floppy. But there is still one major puzzle part missing.

This missing piece is so large and obvious that those who find their MultiRead drives unable to read their CD-RW discs blame the CD-RW recording software, the CD-RW media, the CD-RW recorder, the MultiRead CD-ROM drive, or all four. Increasingly, queries from these puzzled users are showing up in software support listserves, Usenet newsgroups, and in technical support calls.

The answer that all of these users are seeking is native support for the UDF file system, which no currently available operating system offers.

NOT FOR DRIVES ONLY

The problem is an old and familiar one for compact disc--the difference between physical compatibility and logical compatibility. For ten years, evangelists of CD-ROM technology have rhapsodized, "CD-ROM is the most universally standardized technology ever created. With CD-ROM, any disc reads in any drive." Followed, of course, by the fine print, which contains disclaimers, caveats, and explanations of why an ISO 9660 formatted disc that works flawlessly on a DOS or Windows system looks strange or unreadable on a Mac, and vice versa. In other words, it's true that any CD-ROM can be read by any CD-ROM drive. It's also true that any MultiRead drive, by definition, can read any disc with a "CD" prefix. Whether the system hosting the drive has any clue of what to do with the disc's content is another matter entirely.

When a drive maker says a drive conforms to the MultiRead spec and can read CD-RW, that means it is capable of reading the disc physically; i.e., it has AGC (Automatic Gain Control) to compensate for lower reflectivity, and its firmware can handle link blocks without choking. But the MultiRead specification, while it is the first specification for CD-ROM drives, is not limited to making sure drives can physically read discs. The spec also defines a MultiRead operating system, which requires the ability to read UDF version 1.5. According to the MultiRead specification, "The operating system shall support reading of CD-RW discs written with Defect Management according to UDF." Shall, in the language of technical specifications, is used to indicate a requirement, not a recommendation.

In nontechnical specification terms, what is missing in Windows 95, NT, and Macintosh OS 8, is a redirector, similar to MSCDEX or CDFS for ISO 9660, that enables the operating system to recognize and translate a packet-written disc compliant with UDF version 1.5. A UDF redirector will be built into Windows. 98 and NT 5, and into Macintosh OS 8.1, primarily because native UDF support is required for DVD, but there's a distinct possibility that including operating system support for read-only DVD in the UDF format might be as far as Microsoft's or Apple's commitment goes. At question is whether Microsoft or Apple will include UDF version 1.02 support, for read-only DVD, or UDF version 1.5 support, for CD-RW. With version 1.02 support only, neither packet-written CD-R nor CD-RW media not finalized to ISO 9660 will be recognized.

SO WHAT'S HOLDING THINGS UP?

Microsoft "service packs," or OSRs (OEM Service Releases), are software updates released to system OEMs and usually at least partially downloadable from Microsoft's Web site. The most recent, OSR 2, released in September 1996, includes features that will, according to Microsoft, be included in Windows 98. Although OSR 2 includes an enhanced version of CDFS that can handle ISO 9660 volumes up to 4GB, presumably in anticipation of the larger volumes of DVDs, this feature is not downloadable.

"We had anticipated seeing UDF reading capability in Microsoft Windows several months ago, in a service pack release," says Dave Ulmer, director of marketing for Adaptec. In the absence of UDF support from Microsoft, Ulmer says that Adaptec plans to release a UDF reader driver that will allow users to read DirectCD formatted discs in Windows 95 and Windows NT. It will be available from Adaptec's Web site and from some of the company's hardware partners at no charge.

Although there is little doubt that operating system support for CD-RW is desirable and not hard to implement, it's not present in the 2.1 Beta release of Windows 98. Rumors in the beta-testing community are that it will not be in Beta 3.0 either, and there is no mention of CD-RW or UDF 1.5 anywhere on the Microsoft Web site, including online support. But as one beta-tester puts it, "With Microsoft releases, you never really know what's going to be included until you get the software installed." I wonder if it's too much to hope that we'll be pleasantly surprised.