Central Processing Unit (CPU)

The CPU has many levels of caches on the silicon, the fastest being L1 Cache then L2 Cache and then the L3 Cache that is shared by all the CPU cores, it is often better to have data closest to the CPU to benefit from these caches, as they are really fast compared to the Random Access Memory (RAM) which is also pretty fast compared to the Input Output (IO) Devices such as Disks and Universal Serial Bus (USB) sticks