San Jose, Calif. - Mellanox Technologies Inc. is hopping aboard Intel Corp.'s PCI Express bandwagon to roll an Infiniband controller that delivers greater bandwidth and less latency than its existing PCI-X chip and has lower memory requirements. The clustering controller is part of a wave of PCI Express devices and systems expected to hit at the Intel Developer Forum, opening tomorrow in San Francisco.

Mellanox's InfiniHost III EX is a dual-port, 10-Gbit/second Infiniband controller that uses an 8x PCI Express link to deliver aggregate throughput of up to 1.6 Gbytes/s on a single port. That's up from 850-Mbyte/s aggregate throughput on a single port of its previous controller, which was limited by the PCI-X host bus. "There's nothing else out there offering this kind of bandwidth, latency and raw I/Os per second," said Kevin Deierling, vice president of product marketing at Mellanox. The interconnect is aimed at use in server clusters and storage networks.

Mellanox believes PCI Express is opening a route not only to gain clustering bandwidth and trim latency but also to potentially save systems cost.

Thanks to the fast, low-latency Express connection, the InfiniHost III EX will link directly to a server's memory controller rather than a PCI-X bridge chip at speeds that allow the controller to rely on host memory rather than the 128 Mbytes or more of local memory used in Infiniband cards today. That option should be particularly attractive to server blade designs where space is at a premium, said Deierling.

The new "memory-free" option requires a new Express driver. If OEMs don't want that feature, however, they can use existing PCI-X InfiniHost drivers that are compatible with the Express part. Some OEMs are continuing to use a card with local memory tasked for caching read/write acknowledgments and other traffic to optimize systems performance.

One key to delivering a high-performance PCI Express part was finding ways to pipeline and buffer transactions over the interconnect, said Deierling. Mellanox developed its own PCI Express blocks for the design, rather than use third-party intellectual property, he added. "We wanted a solid, stable PCI Express interface back when we started the design about nine months ago. If we had to start a new design today, I imagine we might consider third-party IP for Express," said Deierling.

Mellanox apparently has no active design plans for a version of the controller using the PCI-X 2.0 host bus that some server makers said they favor. To date neither PCI Express nor PCI-X 2.0 has appeared in servers, but Express-based servers are expected to be demonstrated at IDF.

"We'll let the platform makers drive any move into PCI-X 2.0," said Deierling. "We could turn that on very quickly. We have been tracking the interface."

Once seen as a next-generation interconnect for a wide variety of systems, Infiniband is now generally limited to use in clusters and storage networks. In this arena, the interconnect has gained some momentum lately with statements of support from companies including IBM, SGI and Sun Microsystems.

The 27 x 27-mm InfiniHost III EX is made in a 130-nanometer process by Taiwan Semiconductor Manufacturing Co. Ltd. and is sampling now, with production expected by June. Pricing has yet to be set.