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Memory-mapped I/O is preferred in IA-32 and x86-64 based architectures because the instructions that perform port-based I/O are limited to one register: EAX, AX, and AL are the only registers that data can be moved into or out of, and either a byte-sized immediate value in the instruction or a value in register DX determines which port is the source or destination port of the transfer.
The logical address space (that is, the address space available at any moment without changing the memory mapping table) remains limited to 16 bits. Some models, beginning with the PDP-11/45, can be set to use 32K words (64 KB) as the "instruction space" for program code and a separate 32K words of "data space".
Memory-mapped I/O, an alternative to port I/O; a communication between CPU and peripheral device using the same instructions, and same bus, as between CPU and memory; Virtual memory, technique which gives an application program the impression that it has contiguous working memory, while in fact it is physically fragmented and may even overflow ...
In the case of operating systems that support virtual memory, the loader may not actually copy the contents of executable files into memory, but rather may simply declare to the virtual memory subsystem that there is a mapping between a region of memory allocated to contain the running program's code and the contents of the associated ...
It is the fastest and most flexible cache organization that uses an associative memory. The associative memory stores both the address and content of the memory word. [further explanation needed] In the boot process of some computers, a memory map may be passed on from the firmware to instruct an operating system kernel about memory layout. It ...
A memory-mapped file is a segment of virtual memory [1] that has been assigned a direct byte-for-byte correlation with some portion of a file or file-like resource. This resource is typically a file that is physically present on disk, but can also be a device, shared memory object, or other resource that an operating system can reference through a file descriptor.
e820 is shorthand for the facility by which the BIOS of an x86-based computer system reports the memory map to the operating system or boot loader. [1] It is accessed via the int 15h call, by setting the AX register to value E820 in hexadecimal. It reports which memory address ranges are usable and which are reserved for use by the BIOS. [2]
The memory controller manages access to memory using the memory bus or a system bus, or through separate control, address, and data buses, to execute the program's commands. The bus managed by the memory controller consists of multiple parallel lines, each representing a binary digit (bit).