VEMM Device Driver
The Lotus-Intel-Microsoft (LIM) Expanded Memory Specification (EMS) Version
4.0 provides a standard interface for the use of expanded memory on 8086
and 8088 machines. The specification offers up to 32MB of expanded memory
divided into up to 255 objects that can be mapped into conventional memory.
The Virtual Expanded Memory Specification (VEMM) virtual device driver:
Implements all the INT 67H functions in LIM 4.0 EMS,
except those for DMA registers
Provides each virtual DOS machine with its own separate
EMS emulation
Supports remapping of conventional memory for use
by DOS programs
Provides a configurable limit to EMS memory for each
virtual DOS machine
Supports multiple physical to single logical memory
mappings so that different 8086 addresses can be mapped to the same expanded
memory object address.
The VEMM device driver is installed via CONFIG.SYS, with the following syntax
and options:
Syntax
DEVICE=\OS2\MDOS\VEMM.SYS [options]
Options
S=n
EMS memory limit per virtual DOS
machine, with the default being 2048. This can also be set with the
EMS_MEMORY_LIMIT setting in the settings notebook for the
virtual DOS machine.
/L=n
Size
of the remappable conventional memory. This can also be set with the EMS_LOW_OS_MAP_REGION
setting in the settings notebook for the virtual DOS machine.
/H=n
Size of the
extra mappable memory, with the default being 32. This can also be
set with the EMS_HIGH_OS_MAP_REGION setting in the settings notebook
for the virtual DOS machine.
/F=xxxx
Frame
location for remapping expanded memory into conventional memory. The default
is AUTO. This can also be set with the EMS_FRAME_LOCATION setting
in the settings notebook for the virtual DOS machine. The frame location
may need to be moved if there is a conflict with the mapping address of
a physical device driver that does not have a corresponding virtual device
driver. Refer to DOS Settings on how
to use the MEMORY_INCLUDE_REGIONS and MEMORY_EXCLUDE_REGIONS settings
when memory conflicts occur.
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