Enabling Unreal Mode
To enable unreal mode without using any undocumented features of the CPU, the program has to enter protected mode, find or create a flat descriptor in the GDT or LDT, load some of the data segment registers with the respective protected mode "selector", and then switch back to real mode. After returning to real mode, the processor will continue using the cached descriptors as established in protected mode, thus allowing access to 4 GiB of "extended" memory from real mode.
Undocumented features of the CPU, such as LOADALL, can be used to enter unreal mode more quickly.
Read more about this topic: Unreal Mode
Famous quotes containing the words enabling, unreal and/or mode:
“Labor came to humanity with the fall from grace and was at best a penitential sacrifice enabling purity through humiliation. Labor was toil, distress, trouble, fatigue—an exertion both painful and compulsory. Labor was our animal condition, struggling to survive in dirt and darkness.”
—Shoshana Zuboff (b. 1951)
“Writing a novel is not merely going on a shopping expedition across the border to an unreal land: it is hours and years spent in the factories, the streets, the cathedrals of the imagination.”
—Janet Frame (b. 1924)
“Young children learn in a different manner from that of older children and adults, yet we can teach them many things if we adapt our materials and mode of instruction to their level of ability. But we miseducate young children when we assume that their learning abilities are comparable to those of older children and that they can be taught with materials and with the same instructional procedures appropriate to school-age children.”
—David Elkind (20th century)