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Virtual memory combines active RAM and inactive memory on DASD [a] to form a large range of contiguous addresses.. In computing, virtual memory, or virtual storage, [b] is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" [3] which "creates the illusion to users of a very large (main) memory".
The memory subsystem manages the physical memory and the virtual memory of the system (both part of the hardware resource). The virtual memory extends physical memory by using extra space on a peripheral device, usually disk. The memory subsystem is responsible for moving code and data between main and virtual memory in a process known as ...
A 68451 MMU, which could be used with the Motorola 68010. A memory management unit (MMU), sometimes called paged memory management unit (PMMU), [1] is a computer hardware unit that examines all memory references on the memory bus, translating these requests, known as virtual memory addresses, into physical addresses in main memory.
Paged allocation divides the computer's primary memory into fixed-size units called page frames, and the program's virtual address space into pages of the same size. The hardware memory management unit maps pages to frames. The physical memory can be allocated on a page basis while the address space appears contiguous. Usually, with paged ...
The virtual memory is the memory space as seen from a process; this space is often split into pages of a fixed size (in paged memory), or less commonly into segments of variable sizes (in segmented memory). The page table, generally stored in main memory, keeps track of where the virtual pages are stored in the physical memory. This method uses ...
When running a virtual system, it has allocated virtual memory of the host system that serves as a physical memory for the guest system, and the same process of address translation goes on also within the guest system. This increases the cost of memory access since the address translation needs to be performed twice – once inside the guest ...
A system with a smaller page size uses more pages, requiring a page table that occupies more space. For example, if a 2 32 virtual address space is mapped to 4 KiB (2 12 bytes) pages, the number of virtual pages is 2 20 = (2 32 / 2 12). However, if the page size is increased to 32 KiB (2 15 bytes), only 2 17 pages are required. A multi-level ...
The idea behind tmpfs is similar in concept to a RAM disk, in that both provide a file system stored in volatile memory; however, the implementations are different. While tmpfs is implemented at the logical file system layer, a RAM disk is implemented at the physical file system layer. In other words, a RAM disk is a virtual block device with a ...