Editing Memory paging (section)

===Main memory larger than virtual address space===
A few computers have a main memory larger than the virtual address space of a process, such as the Magic-1,<ref name="buzbee" /> some [[PDP-11#Decline|PDP-11]] machines, and some systems using 32-bit [[x86]] processors with [[Physical Address Extension]]. This nullifies a significant advantage of paging, since a single process cannot use more main memory than the amount of its virtual address space. Such systems often use paging techniques to obtain secondary benefits:
* The "extra memory" can be used in the [[page cache]] to cache frequently used files and metadata, such as directory information, from secondary storage.
* If the processor and operating system support multiple virtual address spaces, the "extra memory" can be used to run more processes. Paging allows the cumulative total of virtual address spaces to exceed physical main memory.
* A process can store data in [[memory-mapped file]]s on memory-backed file systems, such as the [[tmpfs]] file system or file systems on a [[RAM drive]], and map files into and out of the address space as needed.
* A set of processes may still depend upon the enhanced security features page-based isolation may bring to a multitasking environment.

The size of the cumulative total of virtual address spaces is still limited by the amount of secondary storage available.