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Mux rolls for serial attached SCSI storage

Posted: 12 Nov 2003 ?? ?Print Version ?Bookmark and Share

Keywords:pmc-sierra? pm8380? quadsmx 3g? fiber channel?

PMC-Sierra Inc. has become one of the first chipmakers to dive into the nascent market for the serial attached SCSI interface. The launch of its PM8380 QuadSMX 3G reflects a growing consensus around existing Fiber Channel storage networks and direct-attached SCSI markets, as opposed to still-emerging Ethernet-based storage.

The bulk of today's back-end storage is based on directly attaching servers to primarily parallel SCSI disks and arrays. PMC-Sierra is betting that market will shift to the recently finalized serial-attached SCSI (SAS). "We see server storage transitioning very aggressively from parallel to serial SCSI over the next two to three years," said Mark Stibitz, GM of PMC's enterprise and storage division, citing a Gartner Dataquest projection that as many as 10M SAS drives could ship by 2006.

The PM8380 QuadSMX 3G is a four-channel, bidirectional 2:1 multiplexer for the 3Gbps SAS standard that leverages the company's high-speed serdes capabilities. The part sports three levels of receiver equalization and four levels of pre-emphasis for signal integrity.

"Our part is basically just a mux, but the value proposition is in how we drive and multiplex a 3Gbps interface with good signal integrity. For server makers this is a major adventure," said Stibitz.

The device sits between an SAS/PCI-X host bus adapter and an array of SAS or serial-ATA (SATA) internal or external drives. It automatically negotiates between 1.5Gbps SATA I and II and 3Gbps SAS interfaces.

The part, made in a 180nm process, consumes an average of 800mW and fits its 11-by-11mm die into a 100-pin BGA package. It sells for $14 in 10,000-unit quantities.

The launch puts PMC out ahead of the first announcements of SAS host bus adapters and drives. But Stibitz said server and array OEMs have quietly committed over the past six months to move to SAS interfaces, driving design momentum. "In two or three months you will see a flurry of product announcements. People are working on extended-array storage boxes that support SATA and SAS as we speak," he said.

PMC-Sierra has also announced five products in less than a year in the Fiber Channel storage segment. Taken together, the news reveals a conservative strategy of focusing on proven Fiber Channel and SCSI markets as the company ekes out a new business in storage after the virtual collapse of the telecom business sector.

"From a product-adoption perspective, we have had several tier-one design wins, and the design activity [in storage] is very high," said Stibitz. He would not quantify the group's revenues to date, however.

One area PMC appears to be avoiding so far is iSCSI, storage networking over the Internet Protocol. The company announced that Trebia Networks used its gigabit/second physical-layer transceiver in the startup's iSCSI reference card. But with the 1Gbps and 2Gbps Ethernet storage market it was pursuing having failed to take off, Trebia has since closed its doors, "You are not seeing any purpose-built components for iSCSI from PMC. I think Fiber Channel and iSCSI will start to converge at the 10Gb level," Stibitz said.

In serdes, PMC has been demonstrating a 6Gb backplane part using a binary approach for almost a year but has yet to announce a product offering. "When you get to 10[Gb], I think the jury is still out on which approach to take," Stibitz said. "We'll try to push binary as far as it can go, but we are working on both approaches."

- Rick Merritt

EE Times





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