DOS/32 Advanced DOS Extender - Utility Programs

6.0 - DOS/32 Advanced - Known Problems

This is not a list of bugs, rather than a list of incompatibility problems that can arise due to the fact that DOS/32 Advanced DOS Extender is written and operates in a completely different way than DOS/4GW. Most of the problems apply to the already written applications that use DOS/4GW (very) specific resources.


Problem 1:
DOS/32 Advanced built-in DPMI does not support selector 0020h (nor any other DOS/4GW specific system selectors), which is used in DOS/4GW as a system selector. Under Clean, XMS and VCPI systems this selector will be unavailable to the applications and any attempt to load value 0020h in any of the segment registers in protected mode will result in a general protection fault exception.

Known effects/incompatibilies:
The game "Top Gun - Fire at will" does not work.


Problem 2:
Some video BIOSes (for example Matrox Mystique/Millenium) return the list of video modes in the VBE information block (INT 10h function AX=4F00h, EDI=ptr to VBE info block). This means that the pointer in the VBE info block at offset 0Eh, *VideoModePtr, is relative to the beginning of the memory and becomes invalid if the structure is moved to other memory locations. DOS/32 Advanced is aware of this and if extended VBE functions are called, will correctly translate the pointer to mode list when transferring the structure from the buffer in low memory to the destination location. However, the structure is then not to be moved unless the user is manually adjusting the pointer.

This problem is not specific to DOS/32 Advanced only and applies to other DOS Extenders, such as DOS/4G(W), PMODE/W and CauseWay, which cannot deal with it correctly.

Known effects/incompatibilities:
The game "Star Gunner" does not work with VESA modes.


Problem 3: -- FIXED!
When using extended Mouse functions (protected mode INT 33h) that install a custom interrupt handler (functions 0014h, 0018h and so on), the handler routine must return with a RETF command, not RET or IRETD. DOS/32 Advanced DOS Extender strictly follows the rules defined in mouse driver documentation for real mode which are valid in protected mode as well.

Known effects/incompatibilities:
The game "Dungeon Keeper" does not work.


Problem 4:
DOS/32 Advanced DOS Extender can not correctly load the last Object with data placed behind it when using LX-style linear executables. An example would be a program linked in LX format with debug information included. The linker will place the debug info data right behind the last Object's data. This will, in some cases, mislead the DOS Extender which will believe that it reads the correct number of bytes. That will not be true, of course, and whatever would be in memory after the last Object's data (most likely the beginning of the BSS segment) will be corrupted.

Some programs, depending on how they are written, will tolerate this and the problem will not show up. However, this is quite a serious problem and you should consider using a workaround when linking your programs in LX format with debug info included.

This problem does not apply to LE/LC-style executables. You can place whatever you want behind the last Object when using those file formats.

Known effects/incompatibilities:
Since there are no DOS/4GW programs that use LX-style executables, there are no incompatibility problems.

Use WATCOM Linker option "SYMFILE" to place the debugging information outside your protected mode application. Consider the following example:

system begin my_program
  option osname='My Program'
  libpath %WATCOM%\lib386
  libpath %WATCOM%\lib386\dos
  debug watcom all
  option stub=stub32a.exe
  option symfile=myprog
  option internalrelocs
  format os2 lx

The linker will create a file myprog.sym containing all the debug info data, instead of binding it to your program. You can also use the "op symfile" line without specifying any file name. Look in your WATCOM docs for more information. Also look into dos32a.lnk file. These lines are actually there, they are only commented out.

Problem 5: -- FIXED!
DOS/32 Advanced built-in DPMI will create non-standard stack frames on exceptions. This problem does not affect most applications because they rely on system which should normally handle exceptions. However, if you attempt to install an exception handler using DPMI functions 0202h and 0203h, you must return from it (if it returns) using an IRETD instruction, not RETF, when running under DOS/32 Advanced ADPMI. You may need to install different exception handlers depending on under which system you run: RAW/XMS/VCPI or DPMI.

Known effects/incompatibilities:
None of tested programs has suffered from this so far.


Problem 6:
DOS/32 Advanced does not do automatical pass-up of interrupts other than INT 08h thru INT 0Fh (ie IRQs 0-7, when PICs are not remapped) as opposed to DOS/4G(W) Extenders which callback any interrupt hooked in protected mode to a protected mode handler in range INT 08h through INT 2Eh. In other words, DOS/32 Advanced will install a real mode IRQ callback only for interrupts INT 08-0Fh which are mapped on IRQs 0-7. The interrupts outside this range, except for INTs 70-77h (IRQs 8-15) which are also auto-callbacked to protected mode, will not be callbacked to protected mode when a protected mode interrupt handler is installed for those.

As DOS/4GW DOS Extender cannot callback IRQs of the slave PIC (IRQs 8-15), some protected mode programs and third party libraries, written to work exclusively with DOS/4GW, will workaround this by installing a protected mode ISR in DOS/4GW auto-passup range, typically INT 18h, and then redirect real mode IRQ vector of the slave PIC to that interrupt. Whenever an IRQ would occur (either in real or protected modes), DOS/4GW will typically pass it down to the real mode, where it will be redirected to that interrupt which is in auto-passup range, which in its turn will callback the IRQ occurred to the proper interrupt service routine.

A simplier and less technical explanation would be: if you are experiencing lockups and/or crashes with a program run under DOS/32A, which was originally written for DOS/4GW Extender, check that your hardware is not configured to issue IRQs in range 8 thru 15, and that the program is not using those hardware interrupts.

PLEASE NOTE: this is *NOT* a problem with DOS/32 Advanced, rather than a problem with older software which were written to workaround DOS/4GW lack of a fully featured DPMI host.

Known effects/incompatibilities:
Lockups at startup of your applications, blank screen and a message "PRESS ANY KEY TO REBOOT" or computer reboots all can be effects caused by this problem. Typical examples of hardware which can cause this problem are: a PnP sound cards with IRQ set in range 8-15 and graphics cards (Matrox) which use IRQ in the same range.

There is no easy workaround for this problem. Try reconfiguring your hardware which uses hardware interrupts in range IRQ 8-15. This can be done quite easily on machines with Plug&Play BIOS, otherwise you will need to mess with jumpers on the card. If you have a third party libraries written for DOS/4GW which cause this problem, contact person/company from which you obtained those to get an updated version which will hopefully solve the problem. It is also possible that running under an external DPMI server will solve the problem.

Problem 7:
When a DOS/32 Advanced application that uses "Start Full-Screen under Windows" feature under Windows 95/98 exits, the desktop image and Windows icons may appear to be messed up. This problem is related to the graphics card driver installed in the system, and has been observed on computers equipped with ATI, STB and Matrox graphics cards. Apparently this seems to be a bug in the Windows, not in the DOS Extender.

Turn off "Start Full-Screen under Windows" feature by using SUNSYS Setup Utility, and change application attributes (by using PIF Editor) to run Full-Screen from within Windows.

Problem 8:
DOS/32 Advanced does not emulate DOS/4G(W) behavior of exclusive volume locking under Windows 95+, which is required by programs that use direct access to disk drives through interrupts INT 13h, INT 25h, INT 26h and INT 21h (IOCTL). Windows 95+ Operating Systems do not allow direct access to disk drives (for protection reasons) and require an application to acquire exclusive volume lock on a drive, before it can directly read or write to that drive. This results in that applications which directly write, read or in any other way directly communicate with disk drives (disk utility programs such as disk defragmenting and partitioning utilities as well as some anti-virus programs fall into this category) will fail when run under DOS/32 Advanced in Windows 95+ protected mode environment.

As a workaround you can run applications that directly access disk drives from the real mode DOS (reboot to Win95+ DOS mode). As to the application developers, you are suggested to manually use exclusive volume locking/unlocking before using interrupts INT 13h, INT 25h, INT 26h or INT 21h (IOCTL) as needed. Refer to MSDN articles on exclusive volume locking (Platform SDK/Windows Base Services/Windows 95 features/Using Windows 95 Features/Exclusive Volume Locking) and description of INT 21h function 440Dh for further information.


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