Microarchitecture
Improvements in chip manufacturing allowed more circuitry to be placed on the same chip, and designers started looking for ways to use it. One of the most common ways was to add an ever-increasing amount of cache memory on-chip. Cache is a very fast memory, memory that can be accessed in a few cycles as compared to what is needed to talk to main memory. The CPU includes a cache controller which automates reading and writing from the cache, if the data is already in the cache it simply "appears," whereas if it is not the processor is "stalled" while the cache controller reads it in.