A customized design of DRAM controller for on-chip 3D DRAM stacking

To address the “memory wall” challenge, on-chip memory stacking has been proposed as a promising solution. The stacking memory adopts three-dimensional (3D) IC technology, which leverages through-silicon-vias (TSVs) to connect layers, to dramatically reduce the access latency and improve the bandwidth without the constraint of I/O pins. To demonstrate the feasibility of 3D memory stacking, this paper introduces a customized 3D Double-Data-Rate (DDR) SDRAM controller design, which communicates with DRAM layers by TSVs. In addition, we propose a parallel access policy to further improve the performance. The 3D DDR controller is integrated in a 3D stacking System-on-Chip (SoC) architecture, where a high-bandwidth 3D DRAM chip is stacked on the top. The 3D SoC is divided into two logic layers with each having an area of 2.5 × 5.0mm², with a 3-layer 2Gb DRAM stacking. The whole chip has been fabricated in Chartered 130nm low-power process and Tezzaron's 3D bonding technology. The simulation result shows that the on-chip DRAM controller can run as fast as 133MHz and provide 4.25GB/s data bandwidth in a single channel and 8.5GB/s with parallel access policy.