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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.
A modern computer operating system usually uses virtual memory to provide separate address spaces or separate regions of a single address space, called user space and kernel space. [1] [a] Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour.
In a computer using virtual memory, accessing the location corresponding to a memory address may involve many levels. In computing, a memory address is a reference to a specific memory location in memory used by both software and hardware. [1] These addresses are fixed-length sequences of digits, typically displayed and handled as unsigned ...
If paging is enabled, the base address in a segment descriptor is an address in a linear paged address space divided into 4 KB pages, so when that is added to the offset in the segment, the resulting address is a linear address in that address space; in IA-32, that address is then masked to be no larger than 32 bits. The result may be looked up ...
In computing, a virtual address space (VAS) or address space is the set of ranges of virtual addresses that an operating system makes available to a process. [1] The range of virtual addresses usually starts at a low address and can extend to the highest address allowed by the computer's instruction set architecture and supported by the operating system's pointer size implementation, which can ...
Address spaces are created by combining enough uniquely identified qualifiers to make an address unambiguous within the address space. For a person's physical address, the address space would be a combination of locations, such as a neighborhood, town, city, or country. Some elements of a data address space may be the same, but if any element ...
The advantages of having an IOMMU, compared to direct physical addressing of the memory (DMA), include [citation needed]: . Large regions of memory can be allocated without the need to be contiguous in physical memory – the IOMMU maps contiguous virtual addresses to the underlying fragmented physical addresses.
In virtual memory implementations and memory management units, a memory map refers to page tables or hardware registers, which store the mapping between a certain process's virtual memory layout and how that space relates to physical memory addresses. In native debugger programs, a memory map refers to the mapping between loaded executable(or ...