More like someone at IBM. The memory map mapped BIOS, video, and PCjr cartridge memory into the upper memory area. Other contemporaneous, non-IBM-compatible x86

More like someone at IBM. The memory map mapped BIOS, video, and PCjr cartridge memory into the upper memory area. Other contemporaneous, non-IBM-compatible x86 systems of the era could relax this restriction. The Tandy 2000 loaded its BIOS from disk (instead of having it in ROM) and ran MS-DOS (indeed, its BIOS API was IBM-compatible even though hardware wise it was not), and could access up to 768K of user memory flat out (896K with aftermarket expansions). This briefly gave it an advantage handling large spreadsheets and the like.