In modern computer architectures, the memory type most closely connected to the processor is the main memory (RAM). This is the memory that the CPU directly accesses for active data and program instructions during execution, and it sits on the memory bus or near the CPU in the memory hierarchy to minimize access latency. Cache memory (L1, L2, L3), while technically separate from main memory and embedded within or very close to the processor, is a smaller, faster layer that stores copies of frequently accessed data from main memory to further reduce access times. So, strictly speaking, the closest directly connected memory to the CPU is the cache, but when considering the broader role of providing the data and instructions the CPU executes, main memory is the primary memory that the CPU frequently interacts with.