Firewire, Firewhy, Firewhen?

Posted on October 01, 1997

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Firewire, Firewhy, Firewhen?

The 1394 ("Firewire") desktop I/O interface promises blazing performance and a bunch of other benefits, but don`t hold your breath. Meanwhile, fire up Ultra ATA.

Ron Levine

Speed, speed, and more speed. New PCs are pushing the limits of system performance. Faster microprocessors, multimedia applications, ballooning file sizes, higher performance hard drives, and the introduction of DVD are all contributing to a growing need for higher speed I/O connections to fully utilize the potential of today`s devices.

Why is speed so important? As component performance improves and audio/visual files become more pervasive, the host-peripheral connection must also improve in order to keep pace. In the storage area, for example, disk drives` internal data rates are getting so fast that the host-to-drive interface is becoming the system bottleneck. As the drives` internal data rates surpass the system`s burst transfer rate, data throughput is strangled and larger buffers are needed to hold data before transferring it to the host CPU. This reduces overall system performance while increasing costs.

By increasing the system`s burst transfer rate, throughput is enhanced, eliminating I/O bottlenecks (especially between the host`s memory and disk drive). Also, faster data transfers over the I/O bus can prevent data stream interruption. These bus improvements enhance overall system performance. Increased transfer speed also means smaller buffer sizes, which reduce costs. To make these improvements a reality, however, a faster I/O interface is required.

The IEEE 1394 implementation of the Firewire interface is being touted as the next-generation standard interface for the PC industry. The specification was accepted as an industry standard by the IEEE in December 1995.

IEEE 1394 is a cross-platform version of the high-speed serial data bus originally introduced as Apple Computer`s alternative to the tangled web of cables required to connect peripherals to PCs.

Firewire has been reworked into an industry-standard digital I/O interface by leading vendors within the IEEE 1394 Working Group.

As defined in the IEEE 1394-1995 specification, Firewire is designed to quickly transfer large amounts of data between computers, peripheral devices, and digital consumer products (e.g., digital camcorders, digital video tapes, and digital video disks). In the storage world, Firewire will improve upon existing SCSI and ATA interfaces; in theory, the new bus provides higher speeds and is less expensive and more user-friendly than existing I/O connections. Users of SCSI-compatible products such as CD-ROMs and disk drives will be among the first to benefit.

The IEEE-1394 specifications make the interface an ideal candidate for use in multimedia applications and for the direct connection of digital consumer products to PCs. With Firewire, all peripherals share a common bus connection--not only to the PC but to each other. The 1394 standard defines a back-plane physical layer (operating at 12.5, 25 or 50 Mbps) and a point-to-point cable-connected bus implementation supporting data rates of 100, 200 and 400 Mbps. Both versions are compatible at the link layer and above.

Firewire Advantages

With these standards in place, Firewire is set to become the scalable, low-cost digital interface of the future that will integrate consumer electronics and PCs. Supporters promise that Firewire will allow simplified cabling and hot swap--ping and provide throughput speeds of 400 Mbps and beyond.

Firewire has the bandwidth capacity to replace most of today`s peripheral buses--not to mention power sourcing capability and support for dynamic reconfiguration. According to Danial Faizullabhoy, vice president of Adaptec`s target and optical peripherals group, additional features of the new bus include:

Guaranteed delivery of multiple data streams through isochronous data transport. (Isochronous data transfer provides guaranteed data transport at a predetermined rate, which is particularly important for multimedia applications.)

The ability to connect up to 63 devices without the need for additional hardware, such as hubs.

Data transfer rates of up to 400 Mbps, with 1.2 GBps speeds in development.

A flexible, six-wire cable.

Complete plug-and-play operation, including hot swapping of "live" devices.

But there are problems. No 1394-compatible storage devices are available yet, but a few manufacturers have developed cables and adapters. For example, Belkin Components is shipping 1394 cables with a short lead-time, but has no plans to develop 1394 peripheral devices, and Adaptec offers a host adapter that supports both SCSI and 1394 buses. Also, Sony is shipping Firewire-enabled digital camcorders, but no computer storage devices.

With PCI host-adapter cards, Apple plans to make system software and hardware support for Firewire available for the Power Macintosh this year and will provide hardware support for Firewire on the motherboard sometime next year. According to Gary Little, senior vice president and general manager of Apple`s Power Macintosh division, "Quickly moving multimedia data and large files in and out of PCs is a key requirement of performance-demanding publishing and media authoring customers."

Although almost all of the industry`s key players (over 40 manufacturers) are said to be "onboard" the Firewire standard, none have shipped a storage product using the IEEE-1394 spec. "Firewire hardware and software will appear late in 1998, with some core logic introductions being available later this year," predicts Martin Reynolds, an analyst with Dataquest, a market research firm in San Jose, CA. "But despite its slow start," says Reynolds, "the 1394 implementation of Firewire will be the dominant interface for connections to DVD, disk drives, and consumer digital products by the year 2001."

1394 challenges Ultra ATA

The main alternative to 1394 is Ultra ATA, which enables the new Ultra DMA/33 protocol pioneered by Quantum and Intel. Although Ultra ATA is being patented by Quantum, the protocol is being licensed at no charge to chip set vendors and major PC and peripheral manufacturers. Virtually all leading PC suppliers have announced plans for systems using the new Ultra ATA interface. Intel has announced that it will support the technology in its future chip sets, and all of the major disk drive manufacturers also support the bus.

"With CPU performance doubling every year and high-speed 32-bit bus architectures delivering more bandwidth, the current ATA disk interfaces were causing disk bottlenecks. A new standard in data transfer was needed," claims Tim Orsley, product planning manager in Quantum`s desktop products storage group.

Intel and Quantum jointly developed the Ultra ATA interface with the DMA/33 protocol. The bus has a burst transfer rate of 33.3 MBps, effectively doubling the older ATA data transfer rate. With the Ultra ATA interface, PC users need less time to boot systems and to open applications. The new interface also includes an improved cyclical redundancy check (CRC) to ensure the integrity of transferred data.

Equally important, the new Ultra ATA standard can be added into a system without the need for termination devices, new cabling, or other hardware changes. In addition, it is compatible with systems using older ATA chip sets and drives. Ultra ATA supports legacy machines in PIO and DMA modes. However, the new DMA/33 protocol must be incorporated into the host system`s chip set, requiring older systems to be upgraded with an Ultra ATA PCI adapter to take advantage of the new features. The bus can be implemented in virtually any new system or existing PC at little extra cost.

According to Quantum`s Orsley, "The Ultra ATA interface is perfect for the new generation of advanced operating systems, real-time video, multimedia, and Internet-based applications." Although not a standard like the IEEE 1394 spec, major vendors industry-wide have endorsed the interface, and Ultra ATA products are shipping.

Quantum`s Fireball ST disk drives, for example, have been shipping since March and the company`s Fireball SE series drives are scheduled for release this month. IBM, Maxtor, Seagate, and Western Digital also offer Ultra ATA desktop hard drives, and Adaptec, CMD Technology, OPTi Inc., Promise Technology, and VIA Technologies have adapter cards that support Ultra ATA.

The 1394 Firewire interface promises to revolutionize the transport of digital data between computers and peripherals. Its isochronous support, allowing low-cost implementation of multimedia interfaces, will make it a popular transport pipe.

But 1394 Firewire is not here yet, andit probably won`t arrive before late next year. While supporters of 1394 are long on promises, they are still short on products.

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Ron Levine is a freelance writer in Carpenteria, CA.

Originally published on .

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