The Serial ATA Working Group published the 1.0 draft of its specification, which will effectively double the bandwidth, or capacity for data, between disk drives--ranging from hard drives to CD-rewritable drives--and other PC components.
Although processors, hard drives and other components have increased in speed and performance at steady rates for years, the conduits that connect these parts have not, which has resulted in the equivalent of traffic jams inside computers.
Serial ATA 1.0 is intended primarily to make sure that disk drives can spit up enough data to keep PCs with 1.4-GHz or faster processors happy.
"The way chips are being designed today, they're getting smaller and they're getting faster, so Serial ATA helps address a number of performance issues," said Jeff Ravencraft, chairman of the Serial ATA Working Group and also a marketing manager at the Intel Architecture Labs.
In addition to Intel, the working group includes several industry heavyweights, such as Dell Computer and IBM.
Double the bandwidth
Serial ATA offers about twice as much bandwidth as the current Parallel ATA standard, known as ATA 100. Serial ATA's first incarnation, dubbed Ultra Serial ATA 1500, will offer a peak bandwidth or transfer rate of 1.5 gigabits per second.
"That basically equates to about 150MB of data per second," Ravencraft said. In comparison, Parallel ATA's ATA 100 offers a peak transfer rate of 100MB per second.
"It's important that the interface keeps pace and in fact stays in front of transfer rates from hard drives," said Tom Pratt, manager of storage technology for Dell's Peripherals Development Group. "Parallel (ATA) is running out of runway. The Serial ATA interface is very forward looking. It was created with a 10-year road map in mind."
In addition, Serial ATA will let each drive communicate directly with the processor. Currently, the different drives must share a common connection.
Serial ATA also will do away with Parallel ATA's familiar ribbon cables. These cables act as arteries for moving data between devices inside the PC. Parallel ATA ribbon cable is about two inches wide and can be only 18 inches long. The Serial ATA cables can be made up to three feet long, allowing for more elaborate routing, which would aid in creating cooler-running PCs.
The largest drawback of Parallel cables--aside from bandwidth--is that they can impede airflow inside some of the smaller PCs, which limits cooling capacity, Ravencraft said. A longer cable effectively will let designers run the connection on the edge of a PC case, rather than across the center.
The working group expects Serial ATA adoption to begin in late 2001 or early 2002. It will be phased in over a long period of time, possibly up to two years, the group has said. During this time, Serial ATA will coexist in the PC market with Parallel ATA. Parallel ATA could be extended for one more generation, but Pratt and Ravencraft say it's unlikely.
Because of its higher cost, Serial ATA will be used first in high-end PCs. Over time, it will migrate into lower-cost PCs and into notebooks, low-end workstations and low-end servers, Ravencraft said.
In addition to Intel, Dell and IBM, the seven primary members of the Serial ATA Working Group include APT Technologies and drive makers Maxtor, Quantum and Seagate Technology. The group also claims about 60 so-called contributors.