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  By Will Wade
EE Times

 SAN MATEO, Calif. Ñ A startup networking chip company has begun sampling a device it claims can increase throughput in the backplane up to tenfold by switching from a parallel architecture to a serial design. AANetcom Inc. plans to begin volume shipments next month and said several top-tier networking vendors are already planning to use its technology for routers, switches and carrier-class telecommunications systems.

 

The new device by the company is the latest ripple in a major wave of Gbit+ serial interconnects, including the InfiniBand switched-fabric serial architecture being developed for high-end servers. "Parallel multidrop buses are reaching their limitations in both frequency and width," said Richard O'Connor, vice president of Tundra Semiconductor (Kanata, Ontario). "Systems need to migrate away from them."

 

AANetcom (San Jose, Calif.) sees the Internet phenomenon as the driving need for making the move to serial. "Because of the Internet's increasing bandwidth requirements, data throughput capacity must double every few months," said Farzin Firoozmand, vice president of marketing. "And as pipes get fatter to homes and offices, the routers have to keep up. But routers and switches with parallel backplanes can't keep up."

 

The basic idea behind parallel backplanes is simple-use multiple data streams running in parallel. Bandwidth can be increased simply by adding new channels. But "The problem is that increasing the number of channels requires more pins, and the maximum number of pins that you can get on a chip is about 1,500 to 1,800," said Lauri Vickers, industry analyst for Cahners In-Stat Group (Scottsdale, Ariz.).

 

Maxed out

 

"The physical limitations of parallel designs have maxed out the bandwidth," said Vickers. Parallel is reaching the end of its capacity, she added, because the ever-increasing need for bandwidth is taxing packaging requirements.

 

The alternative is to use a fast, serial approach. "Instead of using several trains on parallel tracks, our design is like using a very fast bullet train to move data," said Firoozmand. The company's chip, the 21Z01 OctalPHY transceiver, supports up to eight bidirectional channels, each capable of carrying up to 1.56 Gbits/second. The device is produced in a standard CMOS process and runs with 2.5 volts of power.

 

The key to the serial design is the clocking, according to Firoozmand. In parallel architectures, a system clock, typically centralized, sets the pace, while with the serial approach, the clock is embedded in the data stream, and the system is able to move data continuously with no time spent inactive. This allows a serial design to increase total system bandwidth even as the number of channels shrinks.

 

AANetcom's transceiver is also expected to be utilized for Gigabit Ethernet networking systems, where network backbones need to aggregate multiple channels of gigabit-speed data. Firoozmand said one of the main target markets for the product is in line cards for networking systems, especially for fibre channel designs. Running at full-speed, the eight channels on a 21Z01 can deliver total bandwidth of 12.48 Gbit/s. The chip is listed at $48 in 1,000-unit shipments.

 

Bandwidth pursued

 

"I think there will definitely be a healthy market for this technology," said Vickers. "Many of the major vendors are already switching to serial backplanes. Anything that can increase system bandwidth is where the market is going."

 

AANetcom faces competition from Applied Micro Circuits Corp. (San Diego). AMCC has been marketing its own serial backplane products for nearly five years, and also delivers bandwidth of up to 1.6 Gbit/s on its own CMOS-produced four-channel transceivers. While this lags behind AANetcom's eight-channel chip, Jon Siann, director of marketing for datacom products at AMCC, said his company's road map is quite similar, with plans to roll out an eight-channel chip and increase channel throughput to 2.5 Gbit/s later this year.

 

"At the higher speeds, serial architecture is definitely where things are going," he said. While he is bullish on the future prospects for the technology, he notes that a new venture will have its work cut out in establishing itself. "There are several vendors in this field, and it's very competitive."

 

With an eight-channel product available now, Louis Gerhardy, semiconductor analyst for Morgan Stanley Dean Witter in San Francisco, said AANetcom's chip will look attractive to customers. "This is the only eight-port device that I know of right now," he said. "They have a higher level of integration relative to other solutions that are available." However, with a limited product portfolio, he added that the company will need to broaden its offering in the future in order to remain competitive.

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