A Generic, Scalable and Globally Arbitrated Memory Tree for Shared DRAM Access in Real-Time Systems

Abstract—Predictable arbitration policies, such as Time Di-vision Multiplexing (TDM) and Round-Robin (RR), are used to provide firm real-time guarantees to clients sharing a single memory resource (DRAM) between the multiple memory clients in multi-core real-time systems. Traditional centralized imple-mentations of predictable arbitration policies in a shared memory bus or interconnect are not scalable in terms of the number of clients. On the other hand, existing distributed memory intercon-nects are either globally arbitrated, which do not offer diverse service according to the heterogeneous client requirements, or locally arbitrated, which suffers from larger area, power and latency overhead. Moreover, selecting the right arbitration policy according to the diverse and dynamic client requirements in re-usable platforms requires a generic re-configurable architecture supporting different arbitration policies. The main contributions in this paper are: (1) We propose a novel generic, scalable and globally arbitrated memory tree (GSMT) architecture for distributed implementation of several predictable arbitration policies. (2) We present an RTL-level implementation of Accounting and Priority assignment (APA) logic of GSMT that can be configured with five different ar-bitration policies typically used for shared memory access in real-time systems. (3) We compare the performance of GSMT with different centralized implementations by synthesizing the designs in a 40 nm process. Our experiments show that with 64 clients GSMT can run up to four times faster than traditional architectures and have over 51 % and 37 % reduction in area and power consumption, respectively. I