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Flat memory model or linear memory model refers to a memory addressing paradigm in which "memory appears to the program as a single contiguous address space."[1] The CPU can directly (and linearly) address all of the available memory locations without having to resort to any sort of bank switching, memory segmentation or paging schemes.
Memory management and address translation can still be implemented on top of a flat memory model in order to facilitate the operating system's functionality, resource protection, multitasking or to increase the memory capacity beyond the limits imposed by the processor's physical address space, but the key feature of a flat memory model is that the entire memory space is linear, sequential and contiguous.
In a simple controller, or in a single tasking embedded application, where memory management is not needed nor desirable, the flat memory model is the most appropriate, because it provides the simplest interface from the programmer's point of view, with direct access to all memory locations and minimum design complexity.
In a general purpose computer system, which requires multitasking, resource allocation, and protection, the flat memory system must be augmented by some memory management scheme, which is typically implemented through a combination of dedicated hardware (inside or outside the CPU) and software built into the operating system. The flat memory model (at the physical addressing level) still provides the greatest flexibility for implementing this type of memory management.
^Gonzalez, Antonio; Latorre, Fernando; Magklis, Grigorios (2011). Processor Microarchitecture: An Implementation Perspective. Morgan & Claypool Publishers. p. 72. ISBN 9781608454525.
data selectors to address data in memory more efficiently. This has been common practice and often referred to as "flat real mode" or "big real mode". The...
different, the segments do not have different memory protections reflecting this. In the flatmemorymodel all segments (segment registers) are generally...
In computing, the x86 memorymodels are a set of six different memorymodels of the x86 CPU operating in real mode which control how the segment registers...
SASOS should not be confused with a flatmemorymodel, which provides no address translation and generally no memory protection. In contrast, a SASOS makes...
gigabytes or more of system memory, even though any single process can only access 4 GB of it in a 32-bit flatmemorymodel. A process that exceeds its...
segmentation to address memory, not the flatmemorymodel used in many other environments. Segmentation involves composing a memory address from two parts...
operating systems for the 80386 and later x86 processors implement the flatmemorymodel, so they cannot use this capability. There was no "Executable" flag...
[citation needed] Flat addressing is possible by applying multiple instructions, which however leads to slower programs. The memorymodel concept derives...
InfoWorld. Vol. 13, no. 17. p. 21. ISSN 0199-6649. "Q94314: 32-Bit FlatMemoryModel MASM Code for Windows NT". Archived from the original on 13 January...
maps to zero, one, or more than one physical address. Addressability Flatmemorymodel Namespace Virtualization "IPv4 Address Space Registry". Internet Assigned...
be set up to act like it had a flatmemorymodel in protected mode despite the fact that it uses a segmented memorymodel in all modes was arguably the...
BC). However, most pre-Socratics (6th–5th century BC) retained the flat-Earth model. In the early 4th century BC, Plato wrote about a spherical Earth....
of x86 that almost entirely removes segmentation in favor of the flatmemorymodel used by almost all operating systems for the 386 or newer processors...
pools of memory for the CPU and video, slowing access between the two. Furber believed that the Acorn design should have a flatmemorymodel and allow...
since the late 1950s. A flatmemorymodel is assumed, specifically, that the DS and ES segments address the same region of memory. Although partly shadowed...
Rockbox uses a simple kernel, with a flatmemorymodel and single process, letting it run on platforms without a memory management unit. Thin threads run...
Computerworld, November 19, 1990 Flash memory cards en route, InfoWorld, July 29, 1991 IBM. IBM Personal System/2 Model 90 XP 486. 1990-10-30 ([24]). IBM Readies...
Depending on the memorymodel, paged memory functionality is usually hardwired into a CPU/MCU by using a Memory Management Unit (MMU) or Memory Protection Unit...
software continues to use instructions with 32-bit addresses and (in a flatmemorymodel) is limited to 4 gigabytes of virtual address space. Operating systems...
Microkernel, a new graphics subsystem, fully 32-bit system code with a flatmemorymodel, Taligent, and OpenDoc. IBM intended for Workplace OS to run on several...
(PGAS) is a parallel programming model paradigm. PGAS is typified by communication operations involving a global memory address space abstraction that is...
10-digit words, about 17.5 kilobytes, of drum memory (later doubled to 4,000 words, about 35 kilobytes, in the Model 4). In BSD Unix and its descendants, /dev/drum...
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