EMM386

The name EMM386 was used for the expanded memory managers of both Microsoft's MS-DOS and Digital Research's DR-DOS, which created expanded memory using extended memory on Intel 80386 CPUs.

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The technique probably first appeared with the development of CEMM, included with Compaq DOS 3.31 in 1988. Microsoft's version first appeared (as a .SYS device driver) with Windows/386 2.1; the more flexible EMM386.EXE version appeared later in MS-DOS 5.0.

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Just as the other expanded memory managers, EMM386 used the processor's virtual 8086 mode. It also had other functions related to Windows, notably managing the virtualization of DOS windows and acting as the actual protected mode Windows kernel. (See the CEMM article for more information.)

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EMM386 could map memory into unused blocks in the Upper Memory Area, allowing device drivers and TSRs to be "loaded high", preserving precious Conventional memory. (For details, see Upper Memory Area.)

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Expanded memory: Expanded Memory is memory on an IBM PC compatible computer that is used through the Expanded Memory Specification ("EMS") memory paging scheme, enabling access to extra RAM above the 1MB conventional memory area while the processor is in real mode. (This was critically important because MS-DOS ran ...

Microsoft: Microsoft Corporation is the world's biggest software company, with over sixty thousand employees and a physical presence in over sixty countries as of 2005. It was founded in 1975 by Bill Gates and Paul Allen, and is headquartered in Redmond, Washington, USA. Microsoft develops, manufactures, lic...

MS-DOS: Microsoft's disk operating system, MS-DOS was the dominant operating system for the PC compatible platform during the 1980s. It has gradually been replaced on consumer desktop computers with various generations of the Windows operating system....