QBX.EXE "EMS Corrupt" Using Expanded Memory in Windows 3.00 (67364)

SUMMARY

When trying to utilize expanded memory, QBX.EXE (from Microsoft Basic PDS versions 7.00 and 7.10) will have problems running under Microsoft Windows version 3.00 enhanced mode if Windows 3.00 has not set the starting page-frame address for expanded memory. QBX.EXE will try to use expanded memory if it is available, unless the QBX /E:0 switch is used.

For QBX.EXE to successfully use expanded memory, Windows needs to create a consecutive 64K page-frame area in the High Memory Area (HMA), C000 hex to EFFF hex. If this memory area is not available for use by QBX.EXE 7.00, QBX.EXE will give an "EMS corrupt" error message and return to the MS-DOS window, or if run from an application icon, will return back to the Program Manager. QBX.EXE version 7.10 will fail to make use of expanded memory and will not give an error message.

If QBX.EXE fails when trying to use expanded memory, the EMMExclude setting in the [386enh] section of your Windows SYSTEM.INI file may need to be changed. EMMExclude is needed to keep Windows from using the same memory as another device that Windows cannot detect, such as a network card, video card, or parts of BIOS for certain machines. To enable QBX.EXE to work correctly, use the EMMExclude setting for the minimum amount of memory, and try to move the address space used by network and video cards to consecutive addresses starting at C000 hex. Also, if there is an area of memory that you know is NOT in use, then the EMMInclude or EMMPageFrame setting can be used to tell Windows that this area is available for use.

This information applies to Microsoft Basic Professional Development System (PDS) versions 7.00 and 7.10 for MS-DOS.

MORE INFORMATION

(For more information, see the application note "Memory Management Under Windows 3.00," which is available from the Windows Applications Support Group at Microsoft Technical Support.)

Windows 3.00 attempts to determine what other devices are using the address space C000 to EFFF hex before creating the page frame area. Sometimes Windows will not detect that another process is using a section of memory and will try to use that section of memory for itself. The following are symptoms that this may be happening: hanging; Windows immediately returning to the MS-DOS prompt after displaying the Windows logo; or video problems such as garbage on the screen or flashing colors. In this situation, the command EMMExclude is used to prevent Windows from conflicting with other devices.

Also, in some situations Windows will sometimes mistakenly think that a section of memory is in use and will avoid creating the page frame area there. To make sure that Windows uses an area of memory, you can use the EMMInclude command. Also, the EMMPageFrame command can be used to specify the specific area for the expanded memory page frame. EMMPageFrame will only work if Windows thinks that area is available.

The following memory map shows the common usage of each area of memory from A000 to EFFF hex:

Address    Used By                  Common Usage
-------    -------                  ------------

A000-BFFF  Display adapter reserve  EGA and VGA use all, CGA and MDA
                                    use a portion.

C000-DFFF  ROM expansion            Used for I/O channel BIOS.

                                    C000-C3FF: EGA BIOS.
                                    C000-DFFF: many VGA cards use the
                                    whole range.
                                    C600-C63F: PGA communications area.
                                    C800-CBFF: hard disk BIOS.
                                    D000-DFFF: unused.
                                    C800-DFFF: commonly used by
                                    network cards.

E000-EFFF  Expansion of system      Used by many ATs and PS/2s but
           ROM                      not used by other computers.

For example, if you have video card A, which requires address space C000 to C7FF hex, and network card B, which requires C800 to D7FF hex, use the following EMMExclude command:

EMMExclude=C000-D7FF

This should provide enough space for QBX.EXE to use expanded memory.

If it is not possible to move the required HMA for the given applications to consecutive addresses, then you can give multiple EMMExclude commands. For example, if you have an IBM PS/2 that uses E000-EFFF hex for parts of its BIOS area that cannot be moved, and a network card that can use addresses C000 to CFFF or C7FF to D7FF, then you need to use the following EMMExclude commands:

[386enh]
EMMExclude= C000-CFFF
EMMExclude= E000-EFFF

The lower memory area for the network card should be chosen to limit memory fragmentation in the High Memory Area. If you know you are not using the area C800-DFFF and Windows still does not create a page swapping area, then use the EMMInclude command to force Windows to try and use that area of memory. The EMMInclude command overrides the EMMExclude command for the parts of memory that the two statements may have in common:

[386enh]
EMMInclude= C800-DFFF
EMMExclude= C000-CFFF
EMMExclude= E000-EFFF

Instead of using the EMMInclude command, the EMMPageFrame command can be used to tell Windows exactly where to start the page frame area if Windows believes that the specified area is available for use:

[386enh]
EMMPageFrame=C800
EMMExclude= C000-CFFF
EMMExclude= E000-EFFF

Making Windows create a page swapping area may not be possible with some machine configurations. If the above clues do not help create a page frame area, then the Windows Applications Unit of Microsoft Technical Support may have more information about your particular machine configuration and may be able to help you further.

Code Example

The following Basic PDS program will tell you at what address, if any, a page frame has been set. By compiling as shown and running the program in the Windows MS-DOS box, you can determine if and where Windows is creating the expanded memory page frame.

To make a stand-alone executable program out of the following code sample, perform the following steps from the MS-DOS prompt:

BC emspage.bas /o;
LINK emspage.obj,,,QBX.LIB;

'This is the sample program emspage.bas
REM $INCLUDE: 'QBX.BI'
DIM inregs AS regtype
DIM outregs AS regtype
inregs.ax = &H4100
CALL interrupt(&H67, inregs, outregs)
IF (outregs.ax AND &HFF00) = 0 THEN
   PRINT "PAGE FRAME ADDRESS: "; HEX$(outregs.bx)
ELSE
   PRINT "PAGE FRAME ADDRESS: NONE "
END IF