FlexRAM: toward an advanced intelligent memory system

Major advances in merged logic DRAM (MLD) technology coupled with the popularization of memory-intensive applications provide fertile ground for architectures based on intelligent memory (IRAM) or processors-in-memory (PIM). The contribution of this paper is to explore one way to use the current state-of-the-art MLD technology for general-purpose computers. To satisfy requirements of general purpose and low programming cost, we place the PIM chips in the memory system and let them default to plain DRAM if the application is not enabled for intelligent memory. Since wide usability is crucial, we identify and analyze a range of real applications for PIM. Based on the requirements of these applications and current technological constraints, we design a PIM chip and a PIM-based memory system. We call the chip FlexRAM. We describe FlexRAM's design and floorplan, and the resulting memory system. Evaluation of the system through simulations shows that 4 FlexRAM chips often allow a workstation to run 25-40 times faster.