The following text was posted to Slashdot on 16-February-2000 in response to an article about the developing Serial ATA standard. It has been slightly edited from the original posting.

Background: the ATA committee has announced that they are working on a new "Serial ATA" standard, which would replace the bulky 34-conductor IDE cables we all know and love (or hate) with a new high-speed serial interface.

Serial ATA: The Unnecessary Standard

The ideas behind Serial ATA are quite sound. The problem is that there is already an existing standard which accomplishes all that Serial ATA does, and much more, and is not inherently any more expensive.

That standard is IEEE-1394, also known as FireWire or i-Link.

Like Serial ATA, 1394 runs at very high speed over inexpensive cabling consisting of only two pairs of signal lines and one pair for power. The cabling does not impede airflow like parallel ATA cables.

Like Serial ATA, 1394 can be used to transfer data to or from ATA (IDE) interfaces, completely transparently to the host.

Like Serial ATA, 1394 can be (and is) implemented in extremely cheap chips. In fact, there are sub-$5 "tailgate" chips which provide a single-chip 1394-to-ATA adapter. If 1394 was integrated into the drive instead of Parallel ATA, the drive could actually be cheaper than it is now.

UNLIKE Serial ATA, 1394 can also be used to connect SCSI devices, digital cameras, digital audio and video, TCP/IP networking, and many other categories of devices. 1394 already appears to be the interface of choice for most upcoming consumer electronic gear.

UNLIKE Serial ATA, 1394 is already a recognized standard, and work is already underway to extend it to speeds of up to 3.2 Gbps.

UNLIKE Serial ATA, 1394 supports complex topologies: devices with multiple 1394 ports for daisy chaining and hubs. This provides considerable flexibility in how devices are hooked up.

UNLIKE Serial ATA, 1394 supports multiple masters on the same bus.

UNLIKE Serial ATA, 1394 is available NOW, and is already built into some computers.

UNLIKE Serial ATA, 1394 is already supported by Microsoft Windows, and to some extent, Linux.

So why do we need a new standard?

Part of the problem is probably Intel. Initially they announced that they were a supporter of 1394, and that they would build support for it into all of their chipset. They did this with USB, and now it's hard to buy a PC without USB. But when push came to shove, for some reason they didn't do it. Apparently this is due to their work on "USB 2", which pushes the speed of USB into the same range as 1394, but unfortunately still has most or all of the limitations of USB.

Part of the problem is probably Apple. They made ridiculous royalty demands ($1/port), and scared many vendors away. They've since backed down to much more reasonable numbers, but some of the damage was done.

Part of the problem is probably the ATA committee itself. They may be experiencing "NIH" syndrome, preferring to invent a new standard rather than using an existing one, no matter how suited the existing one is.

Part of the problem is just the standard chicken-and-egg question. If computers don't have 1394 interfaces, why should disk manufacturers build 1394 into disk drives? If disk drives don't have 1394, why should computer manufacturers build 1394 into the computers? Of course, serial ATA may have the same problem, but it may be less pronounced. The very fact that serial ATA is less functional may make it an easier sell from a marketing point of view.

What should be done? IMNSHO, they should scrap the development of a new Serial-ATA interface, and adopt 1394 as the official Serial ATA standard.

Update: 1394 to appear on commodity PCs after all?

According to an article in The Register, Via Technologies plans to build 1394 support into their future chipsets. VIA is one of the leading PC chipset vendors, and has gained a lot of ground recently due to Intel's missteps with Rambus.

What about USB 2.0?

My friend Mike asks "What's wrong with USB 2.0 ?"

As a disk interface, it will still be too slow, even for some of today's drives:

Time raw hard drive speed ATA speed 1394 speed USB speed
Today: 400 Mbps (Maxtor DiamondMax VL50)
512 Mbps (Seagate Cheetah X15)
800 Mbps (ATA-100) 400 Mbps 12 Mbps
Future: > 1000 Mbps 1500 Mbps (serial ATA) 3200 Mbps 480 Mbps

Not to mention that USB is not a multi-master bus, and has difficult-to-overcome length limitations.

I'd be hard-pressed to think of a single technical characteristic of USB 2.0 that would make it superior to 1394 as a disk interface.

For a somewhat dated critique of USB 2.0 (from when it was only slated to provide 240 Mbps), see the article USB Two-Point-Oh-My!

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Last updated July 31, 2000

Copyright 2000 Eric Smith

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