What major factor impacts memory access time in a NUMA architecture?

In a Non-Uniform Memory Access (NUMA) architecture, the major factor that impacts memory access time is the processor's location relative to the memory. In NUMA systems, each processor has its own local memory, and accessing this local memory is significantly faster than accessing memory that is local to another processor. This architectural design means that the physical distance between the processor and the memory can lead to different access times.

When a processor accesses its local memory, it experiences lower latency and higher bandwidth compared to when it accesses memory that belongs to another processor. Therefore, understanding the layout of processors and their associated memory is essential in optimizing performance in a NUMA system.

While the number of processors, the size of the memory being accessed, and the type of memory technology can also influence performance, none of these factors directly alter the access time in the way that the relative location of the processor to the memory does. This is why the processor location relative to memory stands out as the major contributing factor in determining memory access time within NUMA architectures.