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The DOS4GW DOS extender
DOS/4GW is Rational Systems' DOS extender that allows the GM VHDL compiler,
linker, and loader to use virtual memory and run in protected mode. This
chapter describes some parameters that can be used to control the operations of
DOS/4GW.
The virtual memory management (VMM) services are controlled by the DOS
environment variable
DOS4GVM. If this variable is not set, then only real memory will be used. To
use virtual memory, the environment variable can be set with
set DOS4GVM=option[#value] { option[#value] }
where option may be one of minmen, maxmem, swapmin, swapinc, swapname,
deleteswap, and virtualsize. The value part should appear with options
that require values. The options have the following meaning.
- minmem
- This option takes a value that is the minimum amount of
real memory that will be allocated by VMM. The default value is 512kb.
- maxmem
- This option takes a value that is the maximum amount of
real memory that will be allocated by VMM. The default value is 4Mb.
- virtualsize
- This option specifies the size of the virtual memory
space desired. The value is specified in number of Kb. The default
value is 16Mb.
- deleteswap
- The VMM will create a file to maintain virtual space.
If this option is specified, the file will be deleted when DOS/4GW exits.
Otherwise, it will not be deleted. If it is not deleted, DOS/4GW will be
loaded quicker the next time it is run.
- swapname
- The name of the file created by DOS/4GW to maintain virtual
memory.
- swapmin
- The initial size of the swap file. The default is the size
of the virtual memory space.
- swapinc
- The size by which the swap file grows as more virtual memory
is used.
All the default values will be used if DOS4GVM is set with the command
set DOS4GVM=1
These same options may also be stored in a file. For example, using the
command
set DOS4GVM=@config.vmc
will cause DOS/4GVM to look for the options in the file config.vmc.
The file may contain one option per line with an = before values instead
of the #. For example, config.vmc might be
! My .vmc file
deleteswap
virtualsize = 8192
which would be the same as
set DOS4GVM=deleteswap virtualsize#8192
Lines beginning with ! are comments. The file should not contain any blank
lines.
There is a utility program, pminfo, included that reports information about
how memory is being utilized by DOS/4GW with the current configuration.