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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 ...
The VGA text buffer is located at physical memory address 0xB8000. [14] Since this address is usually used by 16-bit x86 processes operating in real-mode, it is also the first half of memory segment 0xB800. The text buffer data can be read and written, and bitwise operations can be applied. A part of text buffer memory above the scope of the ...
However, "client" versions of 32-bit Windows (Windows XP SP2 and later, Windows Vista, Windows 7) limit physical address space to the first 4 GB for driver compatibility [16] even though these versions do run in PAE mode if NX support is enabled. Windows 8 and later releases will only run on processors which support PAE, in addition to NX and SSE2.
An example of this kind of use concerned access to memory on early PCs. The original PCs used 8086 or 8088 processors which had the ability to address only 1 MB of memory. A large part of this was occupied by the BIOS and the video card, resulting in only 640 kB of contiguous addressable RAM being available. The memory requirement of many ...
Note that this is more or less the same as base-plus-offset addressing mode, except that the offset in this case is large enough to address any memory location. Example 1: Within a subroutine, a programmer may define a string as a local constant or a static variable. The address of the string is stored in the literal address in the instruction.
A memory address a is said to be n-byte aligned when a is a multiple of n (where n is a power of 2). In this context, a byte is the smallest unit of memory access, i.e. each memory address specifies a different byte. An n-byte aligned address would have a minimum of log 2 (n) least-significant zeros when expressed in binary.
In computing, protected mode, also called protected virtual address mode, [1] is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as segmentation, virtual memory, paging and safe multi-tasking designed to increase an operating system's control over application software.
Dual-ported video RAM (VRAM) is a dual-ported RAM variant of dynamic RAM (DRAM), which was once commonly used to store the Framebuffer in Graphics card, . Dual-ported RAM allows the CPU to read and write data to memory as if it were a conventional DRAM chip, while adding a second port that reads out data.