The memory map of the original 8086 computer with its base and extended memory made the original PC rather straightforward, but also posed countless issues for DOS-based applications as they tried to make use of memory beyond the legacy 1 MB address space. The initial ways to deal with this like EMS, XMS and UMB were rather cumbersome and often impractical, but with the arrival of the 80286 and 80386 processors more options opened up, including protected mode. More interestingly, this led to unreal mode, DOS extenders and the somewhat more obscure LOADALL instruction, as covered by [Julio Merino] in a new article.
This is a companion discussion topic for the original entry at https://hackaday.com/2024/02/09/breaking-through-the-1-mb-barrier-in-dos-with-unreal-mode-and-more/