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.

Related Topics:
Expanded memory - Microsoft - MS-DOS - Digital Research - DR-DOS - Extended memory - Intel 80386

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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.

Related Topics:
CEMM - Windows/386 2.1 - MS-DOS

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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.)

Related Topics:
Virtual 8086 mode - Protected mode - CEMM

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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.)

Related Topics:
Upper Memory Area - TSR - Conventional memory

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