What is NUMA?
Most modern CPU’s, Intel new Nehalem’s and AMD’s veteran Opteron are NUMA architectures. NUMA stands for Non-Uniform Memory Access. Each CPU get assigned its own “local” memory, CPU and memory together form a NUMA node (as shown in the diagram below).
Memory access time can differ due to the memory location relative to a processor, because a CPU can access it own memory faster than remote memory thus creating higher latency if remote memory is required.