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PLX, Mellanox field Express Gen2 chips

Posted: 19 Sep 2007 ?? ?Print Version ?Bookmark and Share

Keywords:PCIe 2.0 chips? 10GbE adapter cards? Express 2.0?

Silicon is on the way using the new PCIe 2.0 standard to plow broader internal data paths for servers, storage systems and graphics. PLX Technology debuted its first family of Express 2.0 switches, and Mellanox Technologies announced Infiniband and 10GbE adapter cards using the interconnect onSept. 17.

The switches and cards come hand-in-hand with new PC chip sets from Intel, and ATI division of Advanced Micro Devices and Nvidia supporting the so-called Gen2 version of Express. Express 2.0 doubles the maximum transfer rate for the link from 2.5 to 5GTransfers/second. Systems using the new chip sets are expected to ship before the end of the year.

"All the key players will have Gen2 chip set in Q4," said Akber Kazmi, a product marketing director at PLX.

Dynamic transition
While computers bulk up, communications systems such as routers and switches are just beginning to shift from GbE to the 2.5GTransfers/s Express 1.1 standard as a control-plane interconnect. "It will take quite awhile before they switch to Gen2," said Kazmi.

Given those dynamics, "we will continue to develop more Express Gen1 products over the next year to fill out our product portfolio, particularly in chips for backplanes and control planes for communications systems," he added.

Express itself is still in transition from the PCI and PCI-X links that once dominated computer systems. Express now represents about a third of the revenues for PLX, a company whose business is primarily based in PCI-based chips

"It won't be to long before Express dominates our revenues," said David Raun, VP of marketing for PLX.

Driving the shift this fall are new parts for Express 2.0. Mellanox is shipping versions of its dual-port 10Gbps Ethernet adapter and dual-port 20Gbps Infiniband adapter using Express 2.0.

The additional bandwidth of the interconnect helps the cards hit or approach their full throughput capabilities. The added throughput translates to a decrease of about 25 percent in latency for the Infiniband cards when transferring 2,000bytes or longer messages.

New capabilities
Existing cards using eight lanes of Express 1.1 were limited to 12.5Gbps throughput. The new cards hit the full 20Gbps capabilities of the Ethernet card and get up to 25Gbps throughput for the Infiniband card.

Both Mellanox and PLX are seeing about a 12 percent power increase with the move to Express 2.0. Mellanox said its cards will initially have a 10-15 percent price premium as well, an adder that will come down over time.

For Mellanox the change only required a firmware upgrade. The company developed its own Serdes integrated in its networking chips and they have long been capable of handling the 5GTransfer Express 2.0 speeds and commands.

For its part, PLX is adding five new Gen2 switches to its product line of 17 PCI switches. "They will all be in flip-chip packages to keep size low and signal integrity high. We didn't want to risk trying this with wire-bond packages," said Kazmi.

The switches range from three-port devices supporting 12 lanes to 12-port devices with 48 lanes of Express. They support the Express 2.0 dual-cast feature that lets incoming traffic from any port be replicated for redundancy to any two outgoing ports.

PLX is seeking a patent on a new read pacing algorithm used in the chips. It lets OEMs manage requests for downstream data to better use bandwidth and eliminate bottlenecks identified by some top OEM customers.

The company has expanded internal buffers from 256 to 2,000Kbytes, added incoming and outgoing parity checks and increased power management capabilities. Latency rises from 110 to 140ns due to more clock cycles needed on the Gen2 Serdes.

PLX used Gen2 Serdes from the Artisan division of ARM combined with a scaled up version of its existing switch architecture. The chips are all sampling now and will be in production early next year at prices ranging from $25 to $75.

- Rick Merritt
EE Times

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