Q67364: QBX.EXE "EMS Corrupt" Using Expanded Memory in Windows 3.00
Article: Q67364
Product(s): See article
Version(s): 7.00 7.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | | mspl13_basic
Last Modified: 9-JAN-1991
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 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.
(For more information, see the application note "Memory Management
Under Windows 3.00," which is available from the Windows Applications
Support Group at Microsoft Product Support Services.)
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
Product Support Services 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 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 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
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