Changes in EMM386.EXE Version 4.45 (MS-DOS 6.0) (93375)

The information in this article applies to:
    Microsoft MS-DOS operating system 6.0

This article was previously published under Q93375


Version 4.45 of the Microsoft expanded memory manager (EMM386.EXE), provided with MS-DOS version 6.0, has the following new features:
    Advanced Upper Memory Scanning
    Expanded and Extended Memory Sharing
    Ability to Provide Upper Memory Regions for Microsoft Windows
    Ability to Load with NOEMS When No Page Frame Is Available
    NOVCPI Switch for Smaller Load Size
    Automatic IBM Token Ring Adapter Detection
    Quiet Loading
    Ability to Provide ROM Shadowing
This article describes these features in detail.


Advanced Upper Memory Scanning

EMM386.EXE can now scan the F000h-F7FFh region when the system read-only memory (ROM) is duplicated between F000h-F7FFh and F800h-FFFFh. Also, EMM386.EXE includes the ROM BASIC area on IBM PS/2 systems.

By default, EMM386.EXE version 4.45 scans the C000-EFFF memory range. EMM386.EXE version 4.44 (which shipped with Windows 3.1) scanned the C600-DFFF memory range, and EMM386.EXE version 4.33 (MS-DOS 5.0) scanned the C800-DFFF memory range.

To enable advanced upper memory scanning, add the HIGHSCAN switch to the DEVICE line for EMM386.EXE in the CONFIG.SYS file.

Expanded and Extended Memory Sharing

Previous versions of EMM386.EXE allocated as much extended memory as possible during the initialization phase. This tied up memory that could otherwise have been used by programs that use expanded memory. EMM386.EXE version 4.45 includes support for dynamic allocation of memory. This means EMM386.EXE can create and make available different types of memory as your system requirements change.

Ability to Provide Upper Memory Regions for Windows

EMM386.EXE version 4.45 includes a new WIN= switch that defines upper memory regions available for use by Windows. These regions are similar to X= regions; memory is not mapped to those areas. But unlike X= regions, Windows (in 386 enhanced mode) can map its own memory into these upper memory regions and make more conventional memory available to MS-DOS-based applications running with Windows.

Ability to Load with No Page Frame

Previous versions of EMM386.EXE do not load if expanded memory support is enabled and there is not enough contiguous available address space for an expanded memory page frame. To support MEMMAKER.EXE, EMM386.EXE 4.45 displays a warning message and continues to load when this situation occurs.

NOVCPI Switch for Smaller Load Size

Previous versions of EMM386.EXE disable both expanded memory and virtual control program interface (VCPI) support when the NOEMS switch is used. EMM386.EXE 4.45 leaves VCPI support enabled by default when the NOEMS option is used, relying on the expanded and extended memory sharing enhancement to supply VCPI memory.

VCPI support can be disabled with the new NOVCPI switch. Using NOEMS and NOVCPI together results in a reduction in the amount of extended memory used by EMM386.EXE.

Token Ring Adapter Detection

EMM386.EXE automatically detects the memory location of IBM Token Ring adapter cards and prevents the mapping of expanded or upper memory over the adapter. The new Token Ring adapter detection can be disabled by using the new NOTR command line switch.

Quiet Loading

By default, EMM386.EXE version 4.45 displays messages only if it encounters an error condition. Adding the /VERBOSE (or /V) switch to the EMM386 line in the CONFIG.SYS file forces EMM386.EXE to display status and error messages while loading.

To display status messages without adding the /V switch, press and hold down the ALT key while EMM386.EXE starts and loads.

For more information on the EMM386.EXE switches, type help emm386 at the MS-DOS command prompt.

Ability to Provide ROM Shadowing

EMM386.EXE version 4.45 includes a new ROM= switch that defines regions of read-only memory (ROM) for EMM386.EXE to "shadow." EMM386.EXE copies the contents of the ROM to extended memory (RAM) and maps the ROM addresses to this memory. Specifying this switch can speed up your system if it does not already use shadow RAM.

Modification Type: Major Last Reviewed: 11/16/1999
Keywords: KB93375