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Interconnects correlate signals across two or more wires

Posted: 05 Nov 2014 ?? ?Print Version ?Bookmark and Share

Keywords:chordal code? Glasswing? interconnect?

Increasing Web traffic and slower network connections make bad news. But here's a good one: a family of chip interconnects targeted at chip-to-chip links leverages an architecture that allows signals to be correlated across more than two wires to achieve higher bandwidth and lower power with excellent signal integrity and low latency. This technology, known as Glasswing, addresses the unique challenges of both substrate and interposer in-package solutions.

Developed by Kandou Bus, the core of the technology is a chordal code that delivers five bits over six correlated wires within each clock cycle. Through a simple yet elegant comparator network, signals are received and translated into bits resulting in much higher overall link throughput.

Chordal code

The figure shows the general form of Kandou's interfaces based on chord signalling. It can be modified to accommodate the specific needs of virtually any chip-to-chip interface. (Source: Kandou Bus)

Depending on the application, the link can run at up to 25GBaud, as well as deliver about 20.8Gbit/s per wire at less than 0.5pJ/bit in a 28nm logic process. These benefits are ideal for very short links (less than 10mm) such as the connection inside a package between a DRAM stack and a controller, the link to an out-boarded high speed SerDes, or the coherency buses of a partitioned multi-core processor. The link can also work over channels up to 25mm in length with slightly more power.

To fully realise the benefits of the Glasswing architecture, Kandou has developed optimised circuits and architectures for all parts of the transmission chain including serialisers, drivers, receivers, CDR units, skew mitigators, equalisers, deserialisers and test circuits.

Kandou's Glasswing product development is underway for the first instantiation of the PHY optimised for in-package links between processor cores. A comprehensive 28nm PHY evaluation package will be available Q3 2015.

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