Getting Rid Of The Grid In Net Switches

HIGH-SPEED ASYNCHRONOUS transfer mode switches that handle voice, video, and data simultaneously are the next big thing in telecommunications. The trouble is, they're expensive. They're based on the "crossbar" design--a grid where rows of input lines cross columns of output lines. And every junction point needs its own computer-chip traffic cop.

Now, MMC Networks Inc. in Santa Clara, Calif., has come up with a new design that it says could cut the cost of ATM switches by 90% within five years. The idea: Get rid of the grid, with all of its chips, and instead use one big bank of shared memory. All the input lines dump their bits into this pool, and the computer tells an output line to pick up its "mail" at a specific digital address.

In the past, designers have shied away from this concept because it seems to require an impossibly wide pathway, or bus, to shuttle bits in and out of the memory. But MMC Chief Executive Prabhat K. Dubey says he has discovered a way to get around that problem. Dubey declines to discuss details while a U.S. patent is pending, but several blue-chip switch manufacturers have already committed to buy MMC's chip sets.

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