Ideally one would desire an indefinitely large memory capacity … We are therefore forced to recognize the possibility of constructing a hierarchy of memories, e

Ideally one would desire an indefinitely large memory capacity … We are therefore forced to recognize the possibility of constructing a hierarchy of memories, each of which has greater capacity than the preceding but which is less quickly accessible. ”Burks, Goldstine, and von Neumann, "Preliminary discussionof the logical design of an electronic computing instrument," 1946.