Supporting Distributed Shared Memory on Multi-core Network-on-Chips Using a Dual Microcoded Controller

Supporting Distributed Shared Memory (DSM) is essential for multi-core Network-on-Chips for the sake of reusing huge amount of legacy code and easy programmability. We propose a microcoded controller as a hardware module in each node to connect the core, the local memory and the network. The controller is programmable where the DSM functions such as virtual-to-physical address translation, memory access and synchronization etc. are realized using microcode. To enable concurrent processing of memory requests from the local and remote cores, our controller features two mini-processors, one dealing with requests from the local core and the other from remote cores. Synthesis results suggest that the controller consumes 51k gates for the logic and can run up to 455 MHz in 130 nm technology. To evaluate its performance, we use synthetic and application workloads. Results show that, when the system size is scaled up, the delay overhead incurred by the controller may become less significant when compared with the network delay. In this way, the delay efficiency of our DSM solution is close to hardware solutions on average but still have all the flexibility of software solutions.