The extended memory manager is also responsible for managing allocations in the high memory area ( HMA ) and the upper memory area ( UMA; also referred to as upper memory blocks or UMBs ).
12.
EMS 3.2 used a 64 KB region in the upper 384 KB ( upper memory area ) divided into four 16 KB pages which could be used to map portions of the expanded memory.
13.
Version 4.0 also introduced 32-bit disk access and could reduce its footprint in conventional memory ( the first 640 kilobytes of memory which was critical to MS-DOS ) by running in upper memory area ( the 384 kilobytes of memory located beyond the conventional memory ).
14.
Since an expansion card such as a video adapter, hard drive controller, or network adapter could use allocations of memory in many of the upper memory areas, configuration of some combinations of cards required careful reading of documentation, or experimentation, to find card settings and memory mappings that worked.
15.
Notably, they could create ordinary memory in unused parts of the upper memory area ( UMA ) ( the high 384 kB of real mode address space ) called upper memory blocks ( UMBs ) and provided tools for loading small programs, typically TSRs inside ( " LOADHI " or " LOADHIGH " ).
16.
The first was the Expanded Memory Specification ( EMS ) which originally allowed memory on an add-on card to be accessed via a 64 KB page frame in the reserved upper memory area . 80386 and later systems could use a virtual 8086 mode ( V86 ) mode memory manager like EMM386 to create expanded memory from extended memory without the need of an add-on card.
17.
This driver added a number of extra features, such as the use of 32-bit code paths when it detected an Intel 80386 or higher CPU, caching capabilities and-in addition to its supporting the use of the Upper Memory Area-also permitted the use of Extended Memory for some of its buffers ( reducing the driver's total footprint in upper memory, albeit at the cost of somewhat reduced speed ).
18.
In 1985 the companies Lotus and Intel introduced Expanded Memory Specification ( EMS ) 3.0 for use in IBM PC compatible computers running MS-DOS . Microsoft joined for versions 3.2 in 1986 and 4.0 in 1987 and the specification became known as Lotus-Intel-Microsoft EMS or LIM EMS . It is a form of bank switching technique that allows more than the 640 KB of RAM defined by the original IBM PC architecture, by letting it appear piecewise in a 64 KB " window " located in the Upper Memory Area.
