Remember that in certain situations more important than overall memory size is memory locality. What can fit in the cache together and stay there longer will speed up a program on a multi-tiered memory system (which is just about everything running). Programs that make wild jumps through the code or that load a large data structure to touch just part of it and overwrite it again can slow the processor caches to a relative crawl. In a low-level language, you can sort of hand-optimize this stuff. In a mid-level language like C you can sort of hint to the compiler and it takes care of most details. In a high-level language, the tools may or may not have much done in this area depending on the language and implementation.