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:
“...for it is God who is at work in you, enabling you both to will and to work for his good pleasure.”
—Bible: New Testament, Philippians 2:13.
“In the one instance, the dreamer ... loses sight of this object in a wilderness of deductions and suggestions ... until ... he finds the incitamentum, or first cause of his musings,... forgotten. In my case, the primary object was invariably frivolous, although assuming, through the medium of my distempered vision, a refracted and unreal importance.”
—Edgar Allan Poe (1809–1849)
“The love of their country is with them only a mode of flattering its master; as soon as they think that master can no longer hear, they speak of everything with a frankness which is the more startling because those who listen to it become responsible.”
—Marquis De Custine (1790–1857)