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EMM386 is the expanded memory manager of Microsoft's MS-DOS, IBM's PC DOS, Digital Research's DR-DOS, and Datalight's ROM-DOS [1] which is used to create expanded memory using extended memory on Intel 80386 CPUs. There also is an EMM386.EXE available in FreeDOS. [2]
Extended memory is located above 1 MB, includes the high memory area, and ends at 16 MB on the Intel 286 and at 4 GB on the Intel 386DX and later. In DOS memory management, extended memory refers to memory above the first megabyte (2 20 bytes) of address space in an IBM PC or compatible with an 80286 or later processor.
IBM, however, created its own expanded-memory standard called XMA. The use of expanded memory became common with games and business programs such as Lotus 1-2-3 in the late 1980s through the mid-1990s, but its use declined as users switched from DOS to protected-mode operating systems such as Linux, IBM OS/2, and Microsoft Windows.
Expanded memory managers such as Quarterdeck's QEMM product and Microsoft's EMM386 supported the expanded memory standard without requirement for special memory boards. On 386 and subsequent processors, memory managers like QEMM might move the bulk of the code for a driver or TSR into extended memory and replace it with a small fingerhold that ...
MS-DOS 7.10 provides 624K free conventional memory and up to 1GB XMS/32MB EMS; assuming unaltered MS-DOS, using HIMEM.SYS and EMM386.EXE without any 3rd party utilities. Thus, QEMM is compatible with MS-DOS 7.10 and Windows 9x and provides slightly more free conventional RAM but it does lower the maximum RAM to 256MB XMS/256MB EMS.
IBM computers had BASIC 1.1 in ROM, and IBM's versions of BASIC used code in this ROM-BASIC, which allowed for extra memory in the code area. BASICA last appeared in IBM PC DOS 5.02, and in OS/2 (2.0 and later), the version had ROM-BASIC moved into the program code.
386 MAX (originally 386 to the Max, later Qualitas MAX) is a computer memory manager for DOS-based personal computers. [1] It competed with Quarterdeck's QEMM memory manager. It was manufactured by Qualitas. BlueMax was a special version designed for the IBM PS/2 with ROM compression to get the most of the Upper Memory Blocks.
Traditionally IBM Mainframe memory has been byte-addressable. This kind of memory is termed "Central Storage". IBM Mainframe processors through much of the 1980s and 1990s supported another kind of memory: Expanded Storage. It was first introduced with the IBM 3090 high-end mainframe series in 1985. [28] Expanded Storage is 4KB-page addressable.