DOS/4GW Configuration Guide
WATCOM International Corporation
Waterloo, Ontario, Canada
1 Configuring DOS/4GW
This chapter explains how to use the DOS4G environment variable to
suppress the banner that is displayed by DOS/4GW at startup. It also
explains how to use the DOS16M environment variable to select the switch
mode setting, if necessary, and to specify the range of extended memory in
which DOS/4GW will operate. DOS/4GW is based on Rational Systems' DOS/16M
16-bit Protected-Mode support; hence the DOS16M environment variable name
remains unchanged.
1.1 Suppressing the DOS/4GW Banner
The banner that is displayed by DOS/4GW at startup can be suppressed by
issuing the following command:
set DOS4G=quiet
Do not insert a space between DOS4G and the equal sign. A space to the
right of the equal sign is optional.
1.2 Changing the Switch Mode Setting
In almost all cases, DOS/4GW programs can detect the type of machine that
is running and automatically choose an appropriate real- to protected-mode
switch technique. For the few cases in which this default setting does
not work we provide the DOS16M DOS environment variable, which overrides
the default setting.
Change the switch mode settings by issuing the following command:
set DOS16M=value
Do not insert a space between DOS16M and the equal sign. A space to the
right of the equal sign is optional.
The table below lists the machines and the settings you would use with
them. Many settings have mnemonics, listed in the column "Alternate
Name", that you can use instead of the number. Settings that you must set
with the DOS16M variable have the notation req'd in the first column.
Settings you may use are marked option, and settings that will
automatically be set are marked auto.
Changing the Switch Mode Setting 1 Chapter 1
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+-------+---------------+-------+----------+-----------------------------------+
| | | |Alternate | |
|Status |Machine |Setting|Name |Comment |
+-------+---------------+-------+----------+-----------------------------------+
|auto |386/486 w/ DPMI|0 |None |Set automatically if DPMI is active|
|req'd |NEC 98-series |1 |9801 |Must be set for NEC 98-series |
|auto |PS/2 |2 |None |Set automatically for PS/2 |
|auto |386/486 |3 |386, 80386|Set automatically for 386 or 486 |
|auto |386 |INBOARD|None |386 with Intel Inboard |
|req'd |Fujitsu FMR-70 |5 |None |Must be set for Fujitsu FMR-70 |
|auto |386/486 w/ VCPI|11 |None |Set automatically if VCPI detected |
|req'd |Hitachi B32 |14 |None |Must be set for Hitachi B32 |
|req'd |OKI if800 |15 |None |Must be set for OKI if800 |
|option |IBM PS/55 |16 |None |May be needed for some PS/55s |
+-------+---------------+-------+----------+-----------------------------------+
The following procedure shows you how to test the switch mode setting.
1. If you have one of the machines listed below, set the DOS16M
environment variable to the value shown for that machine and specify a
range of extended memory. For example, if your machine is an NEC
98-series, set DOS16M=1 @2M-4M. See the section, "Fine Control of
Memory Usage" later in this chapter for more information about setting
the memory range.
+--------------------+---------+
| Machine | Setting |
+--------------------+---------+
| NEC 98-series | 1 |
| Fujitsu FMR-60,-70 | 5 |
| Hitachi B32 | 14 |
| OKI if800 | 15 |
+--------------------+---------+
Before running DOS/4GW applications, check the switch mode setting by
following this procedure:
2. Run PMINFO and note the switch setting reported on the last line of
the display. (PMINFO, which reports on the protected-mode resources
available to your programs, is described in more detail in the
chapter, "Utilities".)
If PMINFO runs, the setting is usable on your machine.
3. If you changed the switch setting, add the new setting to your
AUTOEXEC.BAT file.
Note: PMINFO will run successfully on 286 machines. If your DOS/4GW
application does not run, and PMINFO does, check the CPU type reported on
the first line of the display.
2 Changing the Switch Mode Setting Configuring DOS/4GW
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You are authorized (and encouraged) to distribute PMINFO to your
customers. You may also include a copy of this section in your
documentation.
1.3 Fine Control of Memory Usage
In addition to setting the switch mode as described above, the DOS16M
environment variable enables you to specify which portion of extended
memory DOS/4GW will use. The variable also allows you to instruct DOS/4GW
to search for extra memory and use it if it is present.
1.3.1 Specifying a Range of Extended Memory
Normally, you don't need to specify a range of memory with the DOS16M
variable. You must use the variable, however, in the following cases:
* You are running on a Fujitsu FMR-series, NEC 98-series, OKI
if800-series or Hitachi B-series machine.
* You have older programs that use extended memory but don't follow one
of the standard disciplines.
* You want to shell out of DOS/4GW to use another program that requires
extended memory.
If none of these conditions applies to you, you can skip this section.
The general syntax is:
set DOS16M= [switch_mode] [@start_address [- end_address]] [:size]
In the syntax shown above, start_address, end_address and size represent
numbers, expressed in decimal or in hexadecimal (hex requires a 0x
prefix). The number may end with a K to indicate an address or size in
kilobytes, or an M to indicate megabytes. If no suffix is given, the
address or size is assumed to be in kilobytes. If both a size and a range
are specified, the more restrictive interpretation is used.
The most flexible strategy is to specify only a size. However, if you are
running with other software that does not follow a convention for
indicating its use of extended memory, and these other programs start
before DOS/4GW, you will need to calculate the range of memory used by the
other programs and specify a range for DOS/4GW programs to use.
DOS/4GW ignores specifications (or parts of specifications) that conflict
with other information about extended memory use. Below are some examples
of memory usage control:
Fine Control of Memory Usage 3 Chapter 1
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set DOS16M= 1 @2m-4m Mode 1, for NEC 98-series machines, and use
extended memory between 2.0 and 4.0MB.
set DOS16M= :1M Use the last full megabyte of extended memory, or
as much as available limited to 1MB.
set DOS16M= @2m Use any extended memory available above 2MB.
set DOS16M= @ 0 - 5m Use any available extended memory from 0.0 (really
1.0) to 5.0MB.
set DOS16M= :0 Use no extended memory.
As a default condition DOS/4GW applications take all extended memory that
is not otherwise in use. Multiple DOS/4GW programs that execute
simultaneously will share the reserved range of extended memory. Any
non-DOS/4GW programs started while DOS/4GW programs are executing will
find that extended memory above the start of the DOS/4GW range is
unavailable, so they may not be able to run. This is very safe. There
will be a conflict only if the other program does not check the BIOS
configuration call (Interrupt 15H function 88H, get extended memory size).
To create a private pool of extended memory for your DOS/4GW application,
use the PRIVATXM program, described in the chapter, "Utilities".
The default memory allocation strategy is to use extended memory if
available, and overflow into DOS (low) memory.
In a VCPI or DPMI environment, the start_address and end_address arguments
are not meaningful. DOS/4GW memory under these protocols is not allocated
according to specific addresses because VCPI and DPMI automatically
prevent address conflicts between extended memory programs. You can
specify a size for memory managed by VCPI or DPMI, but DOS/4GW will not
necessarily allocate this memory from the highest available extended
memory address, as it does for memory managed under other protocols.
1.3.2 Using Extra Memory
Some machines contain extra non-extended, non-conventional memory just
below 16MB. When DOS/4GW runs on a Compaq 386, it automatically uses this
memory because the memory is allocated according to a certain protocol,
which DOS/4GW follows. Other machines have no protocol for allocating
this memory. To use the extra memory that may exist on these machines,
set DOS16M with the + option.
set DOS16M=+
Setting the + option causes DOS/4GW to search for memory in the range from
FA0000 to FFFFFF and determine whether the memory is usable. DOS/4GW does
this by writing into the extra memory and reading what it has written. In
4 Fine Control of Memory Usage Configuring DOS/4GW
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some cases, this memory is mapped for DOS or BIOS usage, or for other
system uses. If DOS/4GW finds extra memory that is mapped this way, and
is not marked read-only, it will write into that memory. This will cause
a crash, but won't have any other effect on your system.
1.4 Setting Runtime Options
The DOS16M environment variable sets certain runtime options for all
DOS/4GW programs running on the same system.
To set the environment variable, the syntax is:
set DOS16M=[switch_mode_setting]^options.
Note: Some command line editing TSRs, such as CED, use the caret (^) as a
delimiter. If you want to set DOS16M using the syntax above while one of
these TSRs is resident, modify the TSR to use a different delimiter.
These are the options:
0x01 check A20 line -- This option forces DOS/4GW to wait until the
A20 line is enabled before switching to protected mode. When
DOS/4GW switches to real mode, this option suspends your
program's execution until the A20 line is disabled, unless an
XMS manager (such as HIMEM.SYS) is active. If an XMS manager
is running, your program's execution is suspended until the A20
line is restored to the state it had when the CPU was last in
real mode. Specify this option if you have a machine that runs
DOS/4GW but is not truly AT-compatible. For more information
on the A20 line, see the section, "Controlling Address Line
A20" in this chapter.
0x02 prevent initialization of VCPI -- By default, DOS/4GW searches
for a VCPI server and, if one is present, forces it on. This
option is useful if your application does not use EMS
explicitly, is not a resident program, and may be used with
386-based EMS simulator software.
0x04 directly pass down keyboard status calls -- When this option is
set, status requests are passed down immediately and
unconditionally. When disabled, pass-downs are limited so the
8042 auxiliary processor does not become overloaded by keyboard
polling loops.
0x10 restore only changed interrupts -- Normally, when a DOS/4GW
program terminates, all interrupts are restored to the values
they had at the time of program startup. When you use this
option, only the interrupts changed by the DOS/4GW program are
restored.
Setting Runtime Options 5 Chapter 1
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0x20 set new memory to 00 -- When DOS/4GW allocates a new segment or
increases the size of a segment, the memory is zeroed. This
can help you find bugs having to do with uninitialized memory.
You can also use it to provide a consistent working environment
regardless of what programs were run earlier. This option only
affects segment allocations or expansions that are made through
the DOS/4GW kernel (with DOS function 48H or 4AH). This option
does not affect memory allocated with a compiler's malloc
function.
0x40 set new memory to FF -- When DOS/4GW allocates a new segment or
increases the size of a segment, the memory is set to 0xFF
bytes. This is helpful in making reproducible cases of bugs
caused by using uninitialized memory. This option only affects
segment allocations or expansions that are made through the
DOS/4GW kernel (with DOS function 48H or 4AH). This option
does not affect memory allocated with a compiler's malloc
function.
0x80 new selector rotation -- When DOS/4GW allocates a new selector,
it usually looks for the first available (unused) selector in
numerical order starting with the highest selector used when
the program was loaded. When this option is set, the new
selector search begins after the last selector that was
allocated. This causes new selectors to rotate through the
range. Use this option to find references to stale selectors,
i.e., segments that have been cancelled or freed.
1.5 Controlling Address Line 20
This section explains how DOS/4GW uses address line 20 (A20) and describes
the related DOS16M environment variable settings. It is unlikely that you
will need to use these settings.
Because the 8086 and 8088 chips have a 20-bit address spaces, their
highest addressable memory location is one byte below 1MB. If you specify
an address at 1MB or over, which would require a twenty-first bit to set,
the address wraps back to zero. Some parts of DOS depend on this wrap, so
on the 286 and 386, the twenty-first address bit is disabled. To address
extended memory, DOS/4GW enables the twenty-first address bit (the A20
line). The A20 line must be enabled for the CPU to run in protected mode,
but it may be either enabled or disabled in real mode.
By default, when DOS/4GW returns to real mode, it disables the A20 line.
Some software depends on the line being enabled. DOS/4GW recognizes the
most common software in this class, the XMS managers (such as HIMEM.SYS),
and enables the A20 line when it returns to real mode if an XMS manager is
present. For other software that requires the A20 line to be enabled, use
the A20 option. The A20 option makes DOS/4GW restore the A20 line to the
6 Controlling Address Line 20 Configuring DOS/4GW
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setting it had when DOS/4GW switched to protected mode. Set the
environment variable as follows:
set DOS16M= A20
To specify more than one option on the command line, separate the options
with spaces.
The DOS16M variable also lets you to specify the length of the delay
between a DOS/4GW instruction to change the status of the A20 line and the
next DOS/4GW operation. By default, this delay is 1 loop instruction when
DOS/4GW is running on a 386 machine. In some cases, you may need to
specify a longer delay for a machine that will run DOS/4GW but is not
truly AT-compatible. To change the delay, set DOS16M to the desired
number of loop instructions, preceded by a comma:
set DOS16M=,loops
Controlling Address Line 20 7 Chapter 1
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8 Controlling Address Line 20
2 VMM
The Virtual Memory Manager (VMM) uses a swap file on disk to augment RAM.
With VMM you can use more memory than your machine actually has. When RAM
is not sufficient, part of your program is swapped out to the disk file
until it is needed again. The combination of the swap file and available
RAM is the virtual memory.
Your program can use VMM if you set the DOS environment variable, DOS4GVM,
as follows. To set the DOS4GVM environment variable, use the format shown
below.
set DOS4GVM= [option[#value]] [option[#value]]
A "#" is used with options that take values since the DOS command shell
will not accept "=".
If you set DOS4GVM equal to 1, the default parameters are used for all
options.
Example:
C>set DOS4GVM=1
2.1 VMM Default Parameters
VMM parameters control the options listed below.
MINMEM The minimum amount of RAM managed by VMM. The default is
512KB.
MAXMEM The maximum amount of RAM managed by VMM. The default is 4MB.
SWAPMIN The minimum or initial size of the swap file. If this option
is not used, the size of the swap file is based on VIRTUALSIZE
(see below).
SWAPINC The size by which the swap file grows.
SWAPNAME The swap file name. The default name is "DOS4GVM.SWP". By
default the file is in the root directory of the current
drive. Specify the complete path name if you want to keep the
swap file somewhere else.
DELETESWAP Whether the swap file is deleted when your program exits. By
default the file is not deleted. Program startup is quicker
if the file is not deleted.
VIRTUALSIZE The size of the virtual memory space. The default is 16MB.
VMM Default Parameters 9 Chapter 2
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2.2 Changing the Defaults
You can change the defaults in two ways.
1. Specify different parameter values as arguments to the DOS4GVM
environment variable, as shown in the example below.
set DOS4GVM=deleteswap maxmem#8192
2. Create a configuration file with the filetype extension ".VMC", and
call that as an argument to the DOS4GVM environment variable, as shown
below.
set DOS4GVM=@NEW4G.VMC
2.2.1 The .VMC File
A ".VMC" file contains VMM parameters and settings as shown in the example
below. Comments are permitted. Comments on lines by themselves are
preceded by an exclamation point (!). Comments that follow option
settings are preceded by white space. Do not insert blank lines:
processing stops at the first blank line.
!Sample .VMC file
!This file shows the default parameter values.
minmem = 512 At least 512K bytes of RAM is required.
maxmem = 4096 Uses no more than 4MB of RAM
virtualsize = 16384 Swap file plus allocated memory is 16MB
!To delete the swap file automatically when the program exits, add
!deleteswap
!To store the swap file in a directory called SWAPFILE, add
!swapname = c:\swapfile\dos4gvm.swp
10 Changing the Defaults
Download Driver Pack
After your driver has been downloaded, follow these simple steps to install it.
Expand the archive file (if the download file is in zip or rar format).
If the expanded file has an .exe extension, double click it and follow the installation instructions.
Otherwise, open Device Manager by right-clicking the Start menu and selecting Device Manager.
Find the device and model you want to update in the device list.
Double-click on it to open the Properties dialog box.
From the Properties dialog box, select the Driver tab.
Click the Update Driver button, then follow the instructions.
Very important: You must reboot your system to ensure that any driver updates have taken effect.
For more help, visit our Driver Support section for step-by-step videos on how to install drivers for every file type.