ATAPI vs. SCSI - Technology Information

Emedia Professional, Feb, 2000 by Peter Schworm

Is SCSI facing extinction? When even steadfast SCSI-champion Plextor decides to release an ATAPI CD-RW drive, it's clear that a profound CD-R industry transition has taken place. The company's new 8x4x32 CD-RW bundle signals the end of an era, when the last holdout for SCSI's high-performance guarantee has done what it would have once thought unthinkable, and joined the rest of the industry in taking the ATAPI plunge. By moving to ATAPI, companies are catering to an increasingly low-end, consumer-driven interface market, one in which cost and simplicity concerns outweigh performance. Most industry experts agree that for consumers, who value low cost and ease of use, ATAPI/IDE has overwhelmingly become the interface of choice, although they are still at a loss to say exactly why. "Ail of a sudden, the whole world shifted, almost overnight, to ATAPI," says Dean Quarnstrom of Yamaha. "It was like a herd of wild elephants."

While not expressing it in terms quite so dramatic, Plextor vice president for sales and marketing Howard Wing agrees. "The tremendous growth anticipated for CD-RW will be in the ATAPI market, while the numbers remain flat for SCSI drives," he says. Nonetheless, SCSI remains the interface of choice in professional CD-R markets--particularly in OEM markets like high-end system integration and multidisc duplication--and consequently, Plextor will produce future drives (at 12X and beyond) in both SCSI and ATAPI models.

While the market's shift to ATAPI reflects a movement away from the power-users to mass retail sales, Quarnstrom and others in the industry find this movement somewhat illogical, given that ATAPI costs only slightly less to produce, and trails SCSI in virtually all performance standards.

Jean-Eric Garnier, director of personal computing solutions for principle SCSI-card supplier Adaptec, also attributes the CD-R market's explosive consumer growth as the culprit behind SCSI's declining market share, which David Bunzel of Santa Clara Consulting pegs at 23 percent, compared to 74 percent for ATAPI. "The whole industry has gone to the consumer," says Quarnstrom.

Tony Jasionowski of Panasonic predicts ATAPI's low cost and reasonable performance will allow the interface to maintain its hold on the mass storage market. ATAPI will become more of a factor in the CD-R/RW world in the months to come, he adds.

A full SCSI solution usually costs approximately $120 more than ATAPI, Garnier estimates, largely because of the separate SCSI card, which an ATAPI connection does not require. Therefore, when low cost is the overriding goal, users typically choose ATAPI, analysts say. "Consumers don't know the difference between ATAPI and SCSI," Quarnstrom said. "They know the difference between $179 and $229.

On the other hand, personal users who run multiple memory-intensive applications simultaneously and are in search of even modest performance gains tend to prefer SCSI's superior reliability and speed. "SCSI is always one generation ahead of ATAPI," Garnier says, noting that as Plextor was releasing its 8x4x32x CD-RW drive, the latest SCSI driver had reached 12X speed. "If performance is important to them, they'll choose SCSI." Industry experts note, however, that consumers are often willing to sacrifice performance for lower cost and simpler implementation.

Although ATAPI's architecture makes it a less expensive connector, its design carries inherent limitations. ATAPI/IDE connectors monopolize the system bus, while SCSI's dedicated processor allows more reliable recording by reducing the potential of buffer under-runs, Garnier says.

Garnier adds that in a CD-R duplication benchmark test conducted by XXCal, SCSI's failure rate was 8 percent, compared to 20 percent for an ATAPI CD-R drive, and Mike Mihalik of LaCie says ATAPI 8X was "a real challenge, due to the system performance requirements."

While generally easier to install and configure than SCSI, Jasionowski says, ATAPI is an internal-only interface, and supports only two drives. SCSI can support up to 64 drives and is the only interface that can link up to seven peripherals on a single chain, using one common driver. It also supports a greater number of peripherals than ATAPI, Garnier says, and offers a clear advantage in stressful environments involving multitasking.

Another potential challenger to SCSI looms in IEEE 1394, also known as FireWire (Apple) and i-Link (Sony). IEEE 1394 is a high-speed interface that allows data transfer rates up to 50MB/sec. Yet because the technology is new, experts say that IEEE is compatible with few devices thus far, and remains expensive. With no drives available at this writing, IEEE 1394 is also unproven as a CD-R interface. Mihalik calls 4X IEEE "not very exciting," but that LaCie has plans for an 8X FireWire drive. And while Adaptec remains SCSI's champion, Garnier notes plans to expand beyond it as well.