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RAM limit. The maximum random access memory (RAM) installed in any computer system is limited by hardware, software and economic factors. The hardware may have a limited number of address bus bits, limited by the processor package or design of the system. Some of the address space may be shared between RAM, peripherals, and read-only memory.
3 GB barrier. In computing, the term 3 GB barrier refers to a limitation of some 32-bit operating systems running on x86 microprocessors. It prevents the operating systems from using all of 4 GiB ( 4 × 10243 bytes) of main memory. [ 1] The exact barrier varies by motherboard and I/O device configuration, particularly the size of video RAM; it ...
In operating systems, memory management is the function responsible for managing the computer's primary memory. [1]: 105–208. The memory management function keeps track of the status of each memory location, either allocated or free. It determines how memory is allocated among competing processes, deciding which gets memory, when they receive ...
However, IA-32 processors from the Pentium Pro onward allow a 36-bit physical memory address space, using Physical Address Extension (PAE), which gives a 64 GB physical address range, of which up to 62 GB may be used by main memory; operating systems that support PAE may not be limited to 4 GB of physical memory, even on IA-32 processors.
Memory management unit. 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. In modern systems, programs generally have ...
e. Real mode, also called real address mode, is an operating mode of all x86 -compatible CPUs. The mode gets its name from the fact that addresses in real mode always correspond to real locations in memory. Real mode is characterized by a 20- bit segmented memory address space (giving 1 MB of addressable memory) and unlimited direct software ...
An operating system (OS) is system software that manages computer hardware and software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, peripherals, and other ...
Conventional memory. In DOS memory management, conventional memory, also called base memory, is the first 640 kilobytes of the memory on IBM PC or compatible systems. It is the read-write memory directly addressable by the processor for use by the operating system and application programs. As memory prices rapidly declined, this design decision ...