Elevator-First: A Deadlock-Free Distributed Routing Algorithm for Vertically Partially Connected 3D-NoCs

Abstract

International audienceIn this paper, we propose a distributed routing algorithm for vertically partially connected regular 2D topologies of different shapes and sizes (e.g., 2D mesh, torus, ring). The topologies that are the target of this algorithm are of practical interest in the 3D integration of heterogeneous dies using Through-Silicon-Vias (TSVs). Indeed, TSV-based 3D integration allows to envision the stacking of dies with different functions and technologies, using as an interconnect backbone a 3D-NoC. Intrinsically, 3D topologies have better performances, but yield and active area (and thus the cost) are function of the number of TSVs; therefore, the designs tend to use only a subset of available TSVs between two dies. The definition of blockage free and low implementation cost distributed deterministic routing on this kind of topology is thus of theoretical and practical interests. We formally prove that independently of the shape and dimensions of the planar topologies and of the number and placement of the TSVs, the proposed routing algorithm using two virtual channels in the plane is deadlock and livelock free. We also experimentally show that the performance of this algorithm is still acceptable when the number of vertical connections decreases

A Framework for Scalable TSV Assignment and Selection in Three-Dimensional Networks-on-Chips

“…By contrast with the aforementioned algorithms, Elevator-First [10] does not impose any constraints on the placement or the selection of elevators. By using Elevator-First as a baseline algorithm, we are therefore able to develop generic selection strategies that are not limited by the TSV placement strategy or any algorithm-specific constraints.…”

“…Because such partial topologies require adequate routing algorithms to ensure correct operation and deadlockfreedom, several deadlock-free routing algorithms have already been proposed [10][11][12]. Regardless of which routing rules are applied, since only some of nodes are connected to TSVs, routers need a reliable way to locate the nodes that are vertically connected, commonly referred to as elevators.…”

“…Using Elevator-First [10] as a baseline routing algorithm, we propose a set of scalable, easy to implement elevator assignment strategies, each featuring both the information to be stored in each router and the algorithms used at configuration time 2 VLSI Design and during runtime to select the best elevator. We test and compare all of the proposed solutions in terms of performance through cycle-accurate simulation and demonstrate the scalability of our methods through hardware synthesis.…”

CoBRA: Low cost compensation of TSV failures in 3D-NoC

“…[10] deals with multiple faults in the 3D-NoC architecture with a limited quantity of TSVs; the authors apply deadlock recovery schemes rather than avoiding deadlock. Elevator-first [11] is a routing algorithm which has been proposed for partially connected 3D-NoCs. The elevators for vertical transmission are planned at design time based on the location of TSVs.…”

A Micro-buffered Router Architecture and Deflection Routing Algorithm for Vertically Partially Connected 3D NoC

“…In [5], the vertically partially connected 3D NoC is proposed for the first time, and Elevator-First routing algorithm is proposed. [6] and [7] reduce the hardware cost and power consumption of the router architecture through modifying deadlock avoidance method.…”