"I've seen renewed enthusiasm for penetration of 1394 in the PC space," the traditional venue of USB, said Mark Kirstein, vice president of Cahners In-Stat Group.

In designing new PCs and peripherals, "Product manufacturers will be making a crucial, yes-or-no decision on 1394b over the next two to three months," said Joseph Pinzarrone, vice president of product development at EndPoints Inc. (Bedford, Mass.), a fabless chip company specializing in video imager controllers.

Silicon for 1394b is due by the third quarter, and systems will be rolling out next year.

Maintaining peer-to-peer operation and identical functionality above the link layer with legacy 1394, the new 1394b spec extends the device-to-device interconnect distance to 100 meters. It allows data transfer between devices at 800 or 1,600 Mbits/second, or up to 3.2 Gbits/s, depending on whether copper wiring or fiber is used.

In contrast, the legacy 1394 spec provides 400-Mbit/s data throughput over 4.5 meters, and USB 2.0, released a year ago, transfers data at 12 to 480 Mbits/s over 5 meters.

Some sources see 1394b's speed and distance boost, along with its efficient data transmission, as opening up fresh opportunities beyond 1394's niche in consumer electronics.

The slow uptake of USB 2.0 is part of what's making 1394 look more attractive to system OEMs, observed Curtis Stevens, senior consulting engineer at Phoenix Technologies. "We are seeing accelerated interest in 1394 today," he said.

Indeed, OEMs' quandary over 1394 vs. USB 2.0 "is now coming down to more of a matter of timing," said Pinzarrone of EndPoints. Despite growing interest in USB 2.0 over the last two years, limited support on the PC-host side is prompting some system vendors to "start asking us about 1394 and the upcoming 1394b," he said. Without a USB 2.0-ready host, manufacturers don't have a platform to test their new USB 2.0 peripheral against, he explained, making product introduction riskier.

USB 2.0 is hampered by the fact that Microsoft Corp. is extending only limited support for the spec in its next-generation operating system (see related story). "The initial release of Windows XP features only 1394," said In-Stat's Kirstein.

Further, Intel Corp.'s PC core logic chip set integrated with USB 2.0, designed to go into PC motherboards, won't be on the market until 2002.

Jason Ziller, president and chairman of the USB Implementers Forum Inc. and a technology initiative manager at Intel, said that USB 2.0 significantly improves data throughput performance for storage devices, printers, scanners and digital still cameras — markets where USB 1.1 is dominant today.

USB 2.0's 480-Mbit/s speed, however, is only a tick above what legacy 1394 has been offering for several years, and half the rate of the new 1394b spec, said Max Bassler, chairman of the 1394 Trade Association and director of I/O products, corporate, at Molex Inc.

Networks inside homes, in professional digital studios or on factory floors will use different media, ranging from unshielded twisted-pair wiring to plastic or glass optical fiber, to extend 1394b links to 100 meters, Bassler explained.

Along with speed and distance gains, 1394b "has vastly improved its efficiency," according to Michael Teener, chief technology officer of Zayante Inc. Whereas a legacy 1394 bus is designed to alternate between data transmission and bus arbitration, 1394b can now do both — sending packets and doing clock recovery for bus arbitration — at the same time, Teener said. A newly developed scheme known as Bus Owner Supervisor Selector is designed to let the 1394b bus know instantly which node should go next for data transmission, saving arbitration time.

Another benefit of 1394b, compared with legacy 1394, is its cost. Though the gate count for a 1394b physical-layer (PHY) IC is likely to double to 20,000-25,000 gates, its analog design will be simpler, said Teener. The reduced complexity on the analog side was made possible because 1394b avoids common-mode signaling and bidirectional arbitration signaling. Since a smaller geometry and smaller voltage are applied to the chip, the integration of the PHY and link components for 1394b silicon gets simpler.

As a result, "the cost of 1394b — pure beta only — is cheaper than 1394a," said Teener.

The ability to maintain backward compatibility is another asset that proponents tout in the 1394b spec. "No legacy device is made obsolete," said Bassler.

A port on a 1394 PHY may be implemented either as a legacy mode, beta-mode only, or as a bilingual port, according to the 1394 Trade Association. The bilingual port makes it possible to connect every computer and consumer device that operates in the legacy 1394 mode with new devices based on 1394b. The bilingual ports are designed to negotiate with an attached peer for the best mode of operation.

Backward compatibility extends to firmware, Teener added. "All the firmware written for legacy 1394 devices will work unchanged, because everything above the link layer remains the same," he said.

Uncertainty ahead

There is no question that cost-conscious OEMs — both computer and consumer electronics companies — would prefer a single bus standard to two. But "unfortunately, uncertainty is likely to remain for at least two to three more years," said In-Stat's Kirstein.

Each of the current options has key advantages, he said. For 1394, these include its peer-to-peer architecture and broader anticipated adoption in consumer electronics, Kirstein said. Meanwhile, "the key advantage for USB is PC volume and installed base."

To amend some of the inconveniences caused by USB's inherent master-slave architecture, the USB group is working on a new spec called "USB-on-the-Go," a proposed supplement to USB 2.0. Still in development, it's designed to add limited host functions to peripherals so that a digital still camera, for example, can be directly connected to a printer for a printout, without first uploading a picture to a PC.

Intel's Ziller explained that two key technologies are involved in USB-on-the-Go: a new receptacle connector, called a dual-role device, designed to support a host and a peripheral; and new protocols required to do arbitration and decide which peripheral becomes a temporary host for data transmission. With the spec not expected until the second half of this year, Ziller said that dual-role products won't appear on the market until sometime in 2002.

Nevertheless, USB-on-the-Go promises to "diminish," at least somewhat, the peer-to-peer advantage the 1394 proponents have always claimed, In-Stat's Kirstein said.

The hottest battleground where USB and 1394 continue to compete head to head is expected to be "scanners, printers and digital still cameras," observed Prashant Kanhere, chief executive officer at Zayante.

USB has less chance in standard consumer categories, where 1394 is pretty well entrenched. A few products are beginning to pack USB ports for a mouse or keyboard alongside their 1394 video ports. Among them are high-end cable set-top boxes, such as one from Sony Corp. Likewise, a few digital camcorders feature both interfaces. But USB is unable to send moving pictures, and the USB 1.0 port on those camcorders is used simply as a bus interface for a file transfer to memory cards, said Kunio Tsuzuki, assistant manager for JVC's Home AV Network Business Unit. Tsuzuki said JVC has no plans to use USB in its digital video camcorders.

USB 2.0 also needs content-protection technology if it is to handle copy-protected video material such as Hollywood movies, said Jerome Tjia, design engineering manager of USB products at Philips Semiconductors. However, having drawn a clear line that video applications are not a USB 2.0 product priority, Philips is not developing Digital Transmission Content Protection support for USB 2.0 silicon, he said.

One new battleground 1394 proponents are hoping to enter and ultimately win is so-called "casual storage." When users are randomly hooking up storage devices to a portable unit such as a laptop computer, the bus power generated by 1394 can essentially provide enough juice to run the random-storage devices. "There will be no need for carrying a battery-powered drive or traveling with a number of power bricks for each of your mobile devices," said Zayante's Kanhere.

USB's 2.5-watt power is fine for powering floppies and Zip drives, but it is not enough to drive CD-ROM, much less CD-R, CD-RW, DVD or hard-disk drives, added Teener of Zayante. The 1394 interface provides a maximum power of 30 W per device. Of course, the downside is that 1394 could drain the batteries of a laptop where the casual-storage devices are attached.

Thus, 1394b comes with a standby power mode. When those casual-storage devices are not in operation, they are automatically disconnected. "It shuts down the power, as a power management mechanism built into Windows XP treats an external casual-storage device just like an internal drive," he explained.

On the silicon side, Randy Trost, a manager at Texas Instruments Inc., promised that TI's 1394b silicon will be in the hands of its customers in the third quarter, with 1394b-based systems emerging next year. Agere (formerly Lucent Microelectronics), NEC and Panasonic have prototype 1394b ICs, while physical-layer components such as cables and connectors are available from Molex.