SAN FRANCISCO. — A math professor's observation mushroomed into a startup with two demo chips and three standards efforts. Kandou Bus aims to drive a broad range of chip-to-chip and backplane interconnects down to picojoules/bit rates measured in single digits.
The idea for the company came when a student working on ways to get more bandwidth from a DSL line showed Amin Shokrollahi differential pair traces on a circuit board.
"I asked him what's a differential pair, and he said it's a way of using complementary signals across two wires. I thought this was so inefficient," says Shokrollahi, a professor at the Swiss Polytechnic in Lausanne.
"I told him what I would do, and he said that it was so simple but no one had ever looked at the problem that way. I decided it was time for a company."
So in 2011 with funds from a Swiss agency, Kandou Bus was formed. The name is the term for beehive in Farsi, Shokrollahi's native tongue. Like a beehive, the Kandou approach involves getting all the links bundled in an interface to cooperate and thus send significantly more bits than is possible on today's differential pairs.
Kandou presented a paper and demoed its technology at last week's International Solid-State Circuits Conference (ISSCC) here. The 40nm demo chip sends 12 Gbit/s per wire at less than 4 picojoules/bit, dispersing eight bits across eight wires. Parts of the chip's technology could be adopted for use in memory interfaces or on 2.5D chip stacks.
The startup hopes to tape out before October, in a 28nm process, a 42 Gbit/s SerDes chip that delivers 21 Gbit/s per wire across four wires. Using 12 taps of decision-feedback equalization, it will drive signals a meter through a Megtron-6 board and connectors, consuming 9 picojoules/bit or less.
By early next year, Kandou hopes to have its technology fully characterized for multiple applications. It expects to deliver hard macros that boost data rates or cut power by up to a factor of four. It will ask for royalties that may vary from 1 to 4 percent of the device's average selling price, based on the application.
"The idea of a exploiting something across the communications channel is very interesting, but whether system providers will be able to embrace it with minimal perturbation in their systems is an open question," said Behzad Razavi, a communications expert and professor of electrical engineering at UCLA, speaking in an interview with EE Times at ISSCC.
Next page: Three standards proposals