Leti researchers, working in the “ IRT Nanoelec ” framework, boosted computing power and reduced energy consumption both by stacking chips on top of each other in a single package, and by placing the chips side by side on a silicon interposer. The chips, which have progressed from demonstrator to fabrication-ready, exchange data via a new communications network that is part of the network on chip (NoC) called 3D-NoC.
3D-NoC technology has been demonstrated with a homogeneous 3D circuit that is comprised of regular tiles assembled using a 4 x 4 x 2 NoC. It also features robust and fault-tolerant asynchronous 3D links, and provides 326 MFlit/s @ 0.66 pJ/bit. [Flit = Flow control dig it] It was fabricated in a 65nm CMOS technology using 1,980 TSVs (through-silicon vias – used to implement direct chip-chip ‘vertical’ connections) in a Face2Back configuration.
This second generation 3D-NoC technology has been integrated in the INTACT circuit developed in the IRT Nanoelec framework. The 3D circuit, currently in foundry, combines a series of chiplets fabricated at the 28nm FDSOI node and co-integrated on a 65nm CMOS interposer. The active interposer embeds several lower-cost functions, such as communication through the NoC and system I/Os, power conversion, design for testability and integrated passive components.
The chip requires 20 times less energy for data transmission than chips placed on an conventional circuit board. This new IP is compatible with standard remote direct-memory-access-type software used for data transmission and has likely industrial uses in virtual-server migration applications.
“The steady rise in the number of applications that require high-performance computing creates a demand for new hardware-plus-software communications solutions that improve both performance and energy consumption,” said Denis Dutoit, Leti strategic marketing manager. “This new technology brick makes it possible to transfer data between processors via a network-on-chip delivering more powerful, energy-efficient computing.”