Computer Hardware Terms, Glossary and Dictionary
Extended memory refers to memory above the first megabyte of address space in an IBM PC with an 80286 or later processor. Two types of memory can be added to a PC to increase memory beyond 1MB: expanded memory and extended memory. Extended memory is not directly available in real mode, only through EMS, UMB, XMS, or HMA; only applications executing in protected mode can use extended memory directly. In this case, the extended memory is provided by a supervising protected-mode operating system such as Microsoft Windows.