Computer pioneers have correctly predicted that programmers would want unlimited amounts of memory. An economical solution to this desire is the implementation of a Memory Hierarchical System, which takes advantage of locality and cost/performance of memory technologies. As time has gone by, the technology has progressed, bringing about various changes in the way memory systems are built. Memory systems must be flexible enough to accommodate various levels of memory hierarchies, and must be able to emulate an environment with unlimited amount of memory.