A fully-synthesizable single-cycle interconnection network for Shared-L1 processor clusters

Rahimi, A. and Loi, I. and Kakoee, M.R. and Benini, L.
Design, Automation Test in Europe Conference Exhibition (DATE), 2011.
Shared L1 memory is an interesting architectural option for building tightly-coupled multi-core processor clusters. We designed a parametric, fully combinational Mesh-of-Trees (MoT) interconnection network to support high-performance, single-cycle communication between processors and memories in L1-coupled processor clusters. Our interconnect IP is described in synthesizable RTL and it is coupled with a design automation strategy mixing advanced synthesis and physical optimization to achieve optimal delay, power, area (DPA) under a wide range of design constraints. We explore DPA for a large set of network configurations in 65nm technology. Post placement&routing delay is 38FO4 for a configuration with 8 processors and 16 32-bit memories (8×16); when the number of both processors and memories is increased by a factor of 4, the delay increases almost logarithmically, to 84FO4, confirming scalability across a significant range of configurations. DPA tradeoff flexibility is also promising: in comparison to the maxperformance 16×32 configuration, there is potential to save power and area by 45% and 12% respectively, at the expense of 30% performance degradation.