Running MS-DOS 5.0 EMM386.EXE with VCPI Applications (73627)
The information in this article applies to:
• Microsoft MS-DOS operating system 5.0
This article was previously published under Q73627
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.
| Modification Type: |
Major |
Last Reviewed: |
11/23/1999 |
| Keywords: |
KB73627 |
|