MILPITAS, Calif. — Most major PC makers have decided to put 1394 on the shelf for a while and use the next generation of the venerable ATA interface in future-generation systems. The Ultra ATA/66 interface provides the speed needed for next-generation disk drives, which will give the committees grappling with 1394 time to complete a specification that is fast enough to support disk drives in the next decade.

Eight leading PC makers, including Compaq, Dell, Gateway and IBM, will announce today that they are supporting the next generation of ATA. Several infrastructure suppliers, including all the leading hard-drive suppliers along with chip makers and software companies, have also said they will put their effort into the parallel interface. Ultra ATA/66 was developed by drivemaker Quantum Corp. with input from Intel. It will be licensed to the companies for free.

That pushes the timetable for 1394 adoption out a bit. Many leading companies once said 1394 would be the PC's main peripheral interface at the dawn of the new century, it now appears that the serial link will be little more than an add-on technology for users who want to tie consumer products to their PCs for the next few years.

The slow advance of an 800 Mbits/second version of 1394 may be a key reason for the widespread inertia for the evolution of the ATA interface.

"The standard is not complete, 1394.B is still in the early draft stages," said Steve Wilkins, program director at Quantum Corp. "There are also significant associated costs with 1394."

Those costs are a key problem for PC makers who are attempting to push prices lower every month. The ATA circuitry is routinely included in chip sets, so it's basically free, while 1394 chips require an additional IC. Until there is a good reason to pay for the extra circuitry in both the PC and the drive, PC vendors will probably stick with the ATA interface, many observers predict.

The main costs for Ultra ATA/66 are in the cable and connectors. The driving technology for the faster interface is an 80-wire cable. It doubles the number of wires to provide enough grounding to eliminate crosstalk at the high frequency. Connectors then have to double the number of contacts.

Ultra ATA/66 products should begin appearing next year. The faster data rates will be needed to keep up with the rapid speed increases of hard-disk drives.

"The internal data rate of disk drives is growing at about 40 percent per year, so they will overrun today's version of ATA around the year 2000," Wilkins said. "The lift to 66 Mbytes/second gives us the headroom to continue increasing performance and capacity beyond 2001."

Those in the 1394 community don't predict much acceptance on the motherboard for some time. Instead, they're focusing on external attachment.

"Because of the availability of Ultra ATA/66, we won't see 1394 adopted inside the box as quickly as many of us would have expected," said Peter Johansson, chairman of one of the 1394 work groups and a 1394 consultant at Congruent Software. "Outside the box, this won't have any impact."