528 THE x86 MICROPROCESSORS
15.9.6 | Flat Model
In a ’386 based system, it is not mandatory to use paging and segmentation together. ere is
the option to turn off the paging mechanism that leaves a segmented architecture. However, a
mechanism to turn off segmentation is not inherently present. However, this can be achieved by
programming techniques.
When the 80386 is used to execute software designed for architectures that do not have
segments, it may be expedient to eff ectively ‘turn off ’ the segmentation features of the 80386.
e 80386 does not have a mode that disables segmentation, but the same eff ect can be achieved
by loading the segment registers with selectors for descriptors that have a base addresses of
0, and by setting the limits ...