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DVD-RAM: Large and Looming

In addition to examining DVD-ROM products, we looked at five first-generation DVD-RAM drives, the rewritable kin of DVD-ROM. (A competing standard, DVD+RW, has thus far failed to materialize; the prospect of a standards war initially hindered growth in the writable DVD market, but DVD-RAM now rules the field.) DVD-RAM drives can read DVD-ROM, CD-ROM, CD-R, and CD-RW discs, and they write to their own proprietary 2.6GB-per-side discs. A double-sided (5.2GB) DVD-RAM disc can hold as much data as six or seven CD-ROMs.

Nevertheless, beware of inflated performance claims. Manufacturers advertise a 1X (1.38 MBps) transfer rate, but our testing shows that drives generally write at approximately a third of their claimed speed. This is due in part to a function known as write verification: Unlike CD-RW units, a typical DVD-RAM drive checks every bit of copied data against the original file to ensure that the information has been faithfully reproduced. As a result, the drive spends half the write cycle verifying data integrity.

Interestingly, the QPS Que drive ships with verification disabled, helping it post faster write times than all the other drives we tested, which had verification enabled by default. QPS representatives claim that verification is unnecessary, but Panasonic and other vendors we asked disagree. They point out that the exposure to outside elements can damage the media, and they fear that the budding technology's credibility could be harmed if customers doubt its reliability. Our take: If you plan to use DVD-RAM to store critical data, write verification will ensure that your files are faithfully recorded.

First-generation DVD-RAM drives read discs relatively slowly, in part because the laser must both read and write--sacrificing optimum read performance for versatility. These drives move data from DVDs at 1.38 or 2.8 MBps (1X or 2X, expressed as a DVD X rating), and from CD-ROMs at relatively poky transfer speeds of 2.4 or 3.6 MBps (16X or 24X, in CD-ROM's X rating parlance).

Media compatibility is one problem with DVD-RAM. The discs come packaged in protective cartridges called Type 1 or Type 2. The Type 1 cartridges--which include all double-sided, 5.2GB discs--are sealed and work in DVD-RAM drives only. Type 2 cartridges are more flexible: You can take out the single-sided, 2.6GB disc and run it in a compatible DVD-ROM drive. Unfortunately, of the DVD-ROM drives we reviewed, only the Hitachi and the CenDyne (which uses a Hitachi mechanism) had the capacity to read Type 2 discs.

Power users who intend to install DVD-RAM and CD-RW drives may run into difficulties. Adaptec's Easy CD Creator 4.0x, DirectCD 2.5, and DirectCD 3 behaved erratically on systems that had Write DVD installed as well. An Adaptec representative told us that the company is working on the problem.

Another drawback of DVD-RAM is the price: Four of the five drives we tested cost at least $400: Hitachi's $400 GF-1000, Panasonic's $699 DVD-RAM LF-D102U, Pinnacle's $699 Micro Flex Cinema PC DVD-RAM kit, and QPS's $689 Que DVD-RAM. The lone exception: Creative Labs' PC-DVD RAM 5.2GB, which costs only $300 and captured our Best Buy.

DVD-RAM technology is developing quickly, however. By this July or August, manufacturers expect to ship backward-compatible, second-generation DVD-RAM drives, priced at around $700, that will double their predecessors' performance--writing at speeds of 2X to faster discs that hold 4.7GB per side. Unfortunately, the current batch of DVD-ROM and 1X-DVD RAM drives cannot read the new media.

In-Drive Movie

DVD-video movies are stored on discs in MPEG-2 format, with a built-in compression scheme that retains high visual quality but still demands relatively large files. To play a DVD film, your DVD-ROM drive needs to have either a software MPEG-2 decoder or an expansion card that includes an MPEG-2 decoder chip. The Toshiba SD-M1402 and Utobia DVD-Motion DVD-ROM drives, along with the Pinnacle Micro Flex Cinema PC DVD-RAM drive, offer versions of Sigma Designs' Realmagic Hollywood Plus card. Creative Labs' PC-DVD Encore 8X comes equipped with Creative's own proprietary Dxr3 card.

MPEG-2 decoder cards take over rendering duties from the CPU, helping movies play more smoothly on slower (under 350-MHz) systems, especially if you're working simultaneously in other applications. Try that using a processor-taxing software decoder, and you may encounter choppy playback. Decoder cards also provide audio and video output jacks for your stereo and television. The Hollywood Plus and Dxr3 cards supply outputs for analog stereo, S/PDIF digital audio (for Dolby Digital receivers), composite video and S-Video.

Software MPEG-2 decoders such as CyberLink's PowerDVD 2.55 and InterVideo's WinDVD 2000 rendered movies on our 400-MHz Celeron test system as successfully as their hardware counterparts did, without tying up a card slot or an IRQ number.

Read speed isn't critical to DVD movie playback. Films are recorded to play at 1X, and the drives we tested can read at much higher rates. The speed potential of these drives (up to 16X for the Pioneer DVD-115) is irrelevant to normal playback, although higher read speeds do allow for smoother fast-forwarding.