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Pages of memory from expanded memory hardware were accessible through an addressing window placed into a free area in the UMA space, and by exchanging it for other pages when needed to access other memory. EMS supported 16 MB of space. Using a quirk in the 286 CPU architecture, the high memory area (HMA) was accessible, as the first 64 KB above ...
A space–time trade off can be applied to the problem of data storage. If data is stored uncompressed, it takes more space but access takes less time than if the data were stored compressed (since compressing the data reduces the amount of space it takes, but it takes time to run the decompression algorithm). Depending on the particular ...
Those machines, and subsequent machines supporting memory paging, use either a set of page address registers or in-memory page tables [d] to allow the processor to operate on arbitrary pages anywhere in RAM as a seemingly contiguous logical address space. These pages became the units exchanged between disk and RAM.
When used for swap, zram (like zswap) allows Linux to make more efficient use of RAM, since the operating system can then hold more pages of memory in the compressed swap than if the same amount of RAM had been used as application memory or disk cache. This is particularly effective on machines that do not have much memory.
Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of resource management applied to computer memory.The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when no longer needed.
Early electronic computers had both limited speed and limited random access memory. Therefore, a space–time trade-off occurred. A task could use a fast algorithm using a lot of memory, or it could use a slow algorithm using little memory. The engineering trade-off was therefore to use the fastest algorithm that could fit in the available memory.
On x86-based PCs, extended memory is only available with an Intel 80286 processor or higher. Only these chips can directly address more than 1 megabyte of RAM.The earlier 8086/8088 processors can make use of more than 1 MB of RAM if one employs special hardware to make selectable parts of it appear at addresses below 1 MB.
Different processes do not share a memory space so this discussion does not apply to two programs, each one running in a different process (hence a different memory space). It applies to two or more (software) threads running in a single process (i.e. a single memory space where multiple software threads share a single memory space).