Memory Address - Memory Models

Memory Models

Many programmers prefer to address memory such that there is no distinction between code space and data space (cf. above), as well as from physical and virtual memory (see below) — in other words, numerically identical pointers refer to exactly the same byte of RAM.

However, many early computers did not support such a flat memory model — in particular, Harvard architecture machines force program storage to be completely separate from data storage. Many modern DSPs (such as the Motorola 56000) have 3 separate storage areas — program storage, coefficient storage, and data storage. Some commonly-used instructions fetch from all three areas simultaneously — fewer storage areas (even if there were the same total bytes of storage) would make those instructions run slower.