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Q73627: Running MS-DOS 5.0 EMM386.EXE with VCPI Applications

Article: Q73627
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:5.0
Operating System(s): 
Keyword(s): 
Last Modified: 23-NOV-1999

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The information in this article applies to:

- Microsoft MS-DOS operating system version 5.0 
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SYMPTOMS
========

You are running virtual control program (VCPI) applications under MS-DOS 5.0
with upper memory block support, and the applications do not run in protected
mode.

CAUSE
=====

In EMM386.EXE version 4.20 (which shipped with MS-DOS 5.0), VCPI is turned off
by default.

NOTE: This information applies to EMM386.EXE version 4.20 and earlier. It does
not apply to later versions of EMM386.EXE

WORKAROUND
==========

You must use the RAM switch to run the applications in protected mode. VCPI
applications cannot run in protected mode if the EMM386.EXE NOEMS switch is
used.

MORE INFORMATION
================

For programs to run in protected (80286) mode while a virtual-86 (80386) mode
monitor is running, the two programs need to communicate. This method of
communication is called VCPI.

EMM386.EXE is fully compatible with VCPI-compliant applications; however, VCPI
applications require that some EMS memory is available when running in protected
mode. This means that VCPI applications cannot run unless the RAM switch is used
with EMM386.EXE. If you are using EMS only for VCPI support, you can use RAM in
conjunction with the P0= parameter to specify the presence of only a single 16K
EMS page. This allows EMM386 to use all the remaining memory for UMB support.
The disadvantage of this option is that it makes EMS available without a page
frame, which may confuse applications that always expect a page frame when EMS
is present.

REFERENCES
==========

"Microsoft MS-DOS User's Guide and Reference," version 5.0, pages 605-609.

Additional query words: 5.00

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Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS500
Version           : MS-DOS:5.0

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