Real Mode

Real mode, also called real address mode, is an operating mode of all x86-compatible CPUs Real mode is characterized by a 20 bit segmented memory address space (giving exactly 1 MiB of addressable memory) and unlimited direct software access to all memory, I/O addresses and peripheral hardware. Real mode provides no support for memory protection, multitasking, or code privilege levels. Before the release of the 80286, which introduced Protected mode, real mode was the only available mode for x86 CPUs. In the interests of backwards compatibility, all x86 CPUs start in real mode when reset.

Read more about Real ModeHistory, Addressing Capacity, A20 Line, Switching To Real Mode

Other articles related to "real, mode, real mode, modes":

DOS Memory Management - The 80286 and The High Memory Area
... had the byproduct of allowing slightly more than 1 megabyte (MiB) of memory to be addressed in the "real" mode ... this to access an additional 64 KiB - 16 bytes of memory in real mode ... Real mode software only cared about the area slightly above 1 MiB, so Gate-A20 was enough ...
Windows 3.0 - System Requirements - Memory Modes
... was the only version of Windows that could be run in three different memory modes Real mode, intended for older computers with a CPU below Intel 80286, and corresponding to its real mode Standard mode ... Real mode primarily existed as a way to run Windows 2.x applications ... to be run in standard or 386 enhanced modes (Microsoft Word 1.x however runs in real mode) ...
... set up the CPU to allow access to all memory from real mode, without having to switch it into protected mode (the so-called 'unreal mode') ... of LOADALL, laid out in the book The Design of OS/2, would have been to allow running former real mode programs in 16-bit protected mode, as utilized by Digital Research's ... system to trap segment register reloads as well as attempts at performing real-mode specific "segment arithmetic" and emulate the desired behavior by updating the segment ...
Legacy Mode - Examples
... x86-64 processors can be run in one of two states long mode provides larger physical address spaces and the ability to run 64-bit applications which can use larger virtual ... These processors' legacy mode allows these processors to act as if they were 16 or 32-bit x86 processors with all of the abilities and limitations of them in order to run legacy 16-bi. 32-bit x86 processors themselves have two legacy modes real mode and virtual 8086 mode ...
Switching To Real Mode
... Intel introduced protected mode into the x86 family with the intention that operating systems which used it would run entirely in the new mode and that ... Because of the substantial differences between real mode and even the rather limited 286 protected mode, programs written for real mode cannot run in protected mode ... Therefore, with a wide base of existing real mode applications which users depended on, abandoning real mode posed problems for the industry, and programmers sought a way to switch ...

Famous quotes containing the words mode and/or real:

    I have no scheme about it,—no designs on men at all; and, if I had, my mode would be to tempt them with the fruit, and not with the manure. To what end do I lead a simple life at all, pray? That I may teach others to simplify their lives?—and so all our lives be simplified merely, like an algebraic formula? Or not, rather, that I may make use of the ground I have cleared, to live more worthily and profitably?
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    The book borrower of real stature whom we envisage here proves himself to be an inveterate collector of books not so much by the fervor with which he guards his borrowed treasures and by the deaf ear which he turns to all reminders from the everyday world of legality as by his failure to read these books.
    Walter Benjamin (1892–1940)