Developing Spec Will Speed Disk Drives

SAN FRANCISCO (05/05/2000) - Hard drives keep getting bigger, faster, and cheaper--and often the interface between the drive and the motherboard can't keep up. But a group of more than two dozen vendors of PCs, drives, and interfaces is banding together to write a new specification designed to solve current problems and speed the growth of drive technology.

The SerialATA Working Group is writing a specification to connect various peripherals and removable media that link at increasing speeds. They showed a working demonstration of the technology at the Windows Hardware Engineering Conference in April, but it's not at your local computer store yet. The final SerialATA specification isn't expected until next year, and products won't be available until 2002.

Participating companies include Dell Computer Corp., IBM Corp., Intel Corp., Maxtor, Quantum Corp., and Seagate.

Besides hard drives, SerialATA connects peripherals such as CD-ROM, CD-RW, DVD-ROM, and tape drives, as well as removable media drives such as the Zip and Jaz. However, SerialATA, like the current EIDE interface, will only work with internal devices. Firewire (IEEE-1394) and the upcoming Universal Serial Bus 2.0 are expected to become the standard for external devices.

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SerialATA will come in several stages. Its first release is expected to offer a 150 mbps transfer rate. Most PCs made in the past three years have a hard drive interface called UltraDMA/33 (33 means a maximum data rata of 33 mbps). PCs with the UltraDMA/66 interface are now out, and PCs with the UltraDMA/100 interface are expected to ship this fall, although no supporting drives have been announced yet. SerialATA is expected to eventually nearly double the speed of the UltraDMA/100 interface.

Besides transfer rates, SerialATA differs significantly from current EIDE connections. It's a serial interface instead of the common parallel data transfer. Instead of the 80-wire flat-ribbon cables now used, it offers a round cable about the size of your PC's mouse cable, with an 8-pin connector on each end instead of a 40-pin EIDE connector.

This eliminates the problem of running ribbon cables inside packed PC boxes.

What's more, the small cables let cooling air flow more freely, permitting smaller, more innovative case designs, vendors say. Also, it runs on 3.3 volts, which takes less power than the usual 5 volts.

SerialATA's biggest change is that you can have more than two hard drives on a cable, and you don't need to deal with jumpers on drives. The interface's star topology means a tiny cable will lead directly from the interface to each drive. Theoretically, you could hook up dozens of drives.

Speedy Drive Times

The SerialATA interface is intended to support a new generation of high-speed hard drives. Drive makers are reluctant to predict how drives will perform by the time SerialATA debuts, but drives are packing more and more data onto hard disk platters.

Capacities of 30GB to 40GB are already common, and some of the first 15,000-rpm drives (available only with a SCSI interface) are expected to ship soon.

(Standard EIDE drives currently spin at either 5400 rpm or 7200 rpm, although 10,000 rpm drives are also available in SCSI.) Within a few years, drives with capacities of from 100MB to 200MB will become common, analysts say.

Of course, major interface changes also require a time of transition. Vendors will also address compatibility questions. For now, they plan to develop serial-to-parallel and parallel-to-serial adapters that will let older EIDE drives work on the SerialATA interface. Also, SerialATA drives will work in PCs with the older UltraDMA interfaces, although at drastically lower speeds than the interface can offer.

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