SCSI Association Ratifies Ultra3 Spec

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September 15, 1998 (12:00 AM EDT)

The SCSI Trade Association (STA) ratified Ultra3 SCSI's features Monday, promising value-added resellers and integrators improved data throughput and reduced system overhead compared with current small computer system interface (SCSI) standards.

And in an effort to prevent confusion over which features Ultra3 SCSI products include, a group of vendors unveiled an initiative to ensure resellers and integrators their Ultra3 SCSI products include certain features regardless of final implementation.

Ultra3 SCSI will differ in five key areas from Ultra2 SCSI, according to STA officials.

First, transition clocking doubles data throughput to 160 megabytes per second. This is done by sending two pieces of data per clock pulse instead of one, thereby doubling the throughput without increasing the processor's clock speed.

Cyclic redundancy check will improve data-transmission reliability via an enhanced error-catching scheme.

"This can help when hot-plugging devices, where things can get wild and crazy electrically," said Skip Jones, STA vice president and director of planning and technology at QLogic, in Costa Mesa, Calif.

Domain validation lets the host and device communicate to find the optimal data speed, and identifies the topology and configuration of the SCSI bus. This allows plug and play in low-end products while maintaining the integrity of enterprise systems, Jones said.

The other new features include packetization for transferring multiple commands and threads of data per cycle, and quick arbitration select to reduce disconnect and reconnect time on the bus.

Ultra3 SCSI will be backward-compatible with Ultra2 SCSI, allowing Ultra2 SCSI devices to connect to the bus without affecting performance.

A few Ultra3 SCSI products may be available sometime next year. "But original equipment manufacturers see products really becoming available in 2000," said Harry Mason, STA president and director of host marketing for LSI Logic, in Milpitas, Calif.

Michael Casey, research director at Gartner Group, in Stamford, Conn., said Ultra3 SCSI will not slow down the adoption of Fibre Channel.

"As soon as Dell and other server companies offer Fibre Channel, it relegates SCSI to the back end of storage," said Casey. "The trend on the host side is to move to Fibre Channel. Ultra3 SCSI will enable SCSI to continue on the storage side."

While five new features were introduced as part of the Ultra3 SCSI initiative, vendors are free to pick and choose which features to include in their products. For example, a tape-drive vendor might want to use Ultra3 SCSI's high speed, but not need the other features, Jones said.

To ensure compatibility among products from different vendors, the Ultra 160/m SCSI initiative was also released Monday. It is a subset of the Ultra 3 SCSI specification.

Products sporting the Ultra 160/m SCSI logo will offer the double transition clocking, cyclical redundancy checking, and domain validation features.

Ultra 160/m SCSI products are expected next year from LSI Logic, QLogic, Adaptec, Fujitsu Computer Products of America, Mylex, Quantum, and Hewlett-Packard.

Ted Deffenbaugh, Quantum's director of strategic technology, called Ultra 160/m SCSI an open standard. "We have talked to other vendors in the industry. I predict others will announce compliance in the months to come."

Patrick McGarrah, program director of technology at Quantum, agreed that hard-disk and tape-drive vendors will comply with Ultra 160/m SCSI.