Intel 64 and IA-32 Architectures Software Developers Manual Volume 1, Basic Architecture

Vol. 1 3-9
BASIC EXECUTION ENVIRONMENT
segment prevents the stack from growing into the code or data space and
overwriting instructions or data, respectively.
• Real-address mode memory model — This is the memory model for the Intel
8086 processor. It is supported to provide compatibility with existing programs
written to run on the Intel 8086 processor. The real-address mode uses a specific
implementation of segmented memory in which the linear address space for the
program and the operating system/executive consists of an array of segments of
up to 64 KBytes in size each. The maximum size of the linear address space in
real-address mode is 2
20
bytes.
See also: Chapter 15, “8086 Emulation,” Intel® 64 and IA-32 Architectures
Software Developer’s Manual, Volume 3A.
Figure 3-3. Three Memory Management Models
Linear Address
Flat Model
Linear
Address
Space*
Segment Selector
Offset
Segment Selector
Segmented Model
Real-Address Mode Model
Linear Address
Logical
Offset (effective address)
Space Divided
Into Equal
Sized Segments
Address
Logical
Address
Linear
Address
Space*
Segments
* The linear address space
can be paged when using the
flat or segmented model.