Entry control in network-on-chip for memory power reduction

As high-end mobile embedded systems become data-intensive, the off-chip memory is becoming a major contributor to the total energy consumption. Especially, high-end mobile chips accommodate dedicated hardware blocks, e.g., codec and 3D graphics IP's, required for both performance and power consumption reasons. Those IP's usually do not have a large shared memory on chip. Thus, they communicate with each other via the off-chip DDR memory increasing off-chip memory accesses, which increases memory energy consumption during read/write operations. In this paper, we present a method of reducing memory energy consumption during read/write operations. It aims at minimizing the number of row opens and closes, which are the major source of energy consumption during read/write operations. The basic idea is to apply network entry control to prioritize consecutive open row memory accesses. The experimental results show up to 35% reduction in memory energy consumption with an industrial strength multimedia mobile SoC.