Handling the problems and opportunities posed by multiple on-chip memory controllers

Modern processors such as Tilera's Tile64, Intel's Nehalem, and AMD's Opteron are migrating memory controllers (MCs) on-chip, while maintaining a large, flat memory address space. This trend to utilize multiple MC's will likely continue and a core or socket will consequently need to route memory requests to the appropriate MC via an inter- or intra-socket interconnect fabric similar to AMD's HyperTransport(TM), or Intel's Quick-Path Interconnect(TM). Such systems are therefore subject to non-uniform memory access (NUMA) latencies because of the time spent traveling to remote MCs. Each MC will act as the gateway to a particular piece of the physical memory. Data placement will therefore become increasingly critical in minimizing memory access latencies.