32 Bit DOS Protected Mode Application

[Gunther]

Attached to this post is the file pmexamp.zip. It's a 32-bit DOS protected mode program. It's written with JWASM for DOS, but should also work with MASM.
I linked the OBJ files with TLINK, but other linkers should do the job as well. In this case, the batch file must be modified accordingly. Therefore I've attached
the binary files to the archive in case someone doesn't have the used software available.

The source files are PMSHELL.ASM (32-bit DPMI Shell) and examp1.asm (the DOS program). The application outputs some information about the available memory,
then fills a memory area over 1 MB with values and finally displays them on the screen. The program is tested under different virtual machines (DOSBox, VirtualBox,
VMwarePlayer) and under native DOS. I used Japhet's DOS Extender HX, which I can only recommend.

The test under other configurations is interesting for me. I thank you already now for your help.

[Gunther]

I have again a similar situation as in July 2013. On my old machine, the program can request 3.5 GB of RAM with HX.
The new machine only allows 1.2 GB. This will be sufficient in most cases. But what is the cause of this behavior?

I suspect that the hardware manufacturers have installed memory holes again.
That's what xmsstat brings.

Code Select Expand


XMS call address: FFFF:3253
XMS version: 3.0
HMA handled by XMS host, HMA is allocated
largest free memory block (v2) in kB: 65535, total free: 65535
largest free memory block (v3) in kB: 871464, total free: 1228748
XMS handle table at FFFF:34F8, handle cnt/size=48/10
XMS handle array at FFFF:3318

no handle region            size(kB) locks flags
--------------------------------------------------------
  1 3318   00110000-35419FFF   871464     0 01 free
  2 3322   3A317000-4FFFFFFF   357284     0 01 free
--------------------------------------------------------
                              1228748
free handles: 46
no UMB handler installed


Hopefully this will be some help to Japheth. Thank you.

[HSE]

Hi Gunther!

I try in DOSBox-X but look it have a problem to set path. LATER: path in config file is working, and exactly same DosBox result.

No problem in DosBox:

[Gunther]

HSE,

thank you for trying the program under DOSBox. It works as expected.

Did you reassemble or used the attached EXE?

[HSE]

Hi gunther!

It works as expected.

Yes. Could be different in DOSBox-X, but apparently is the same.

Did you reassemble or used the attached EXE?

Attached EXE. Evidently I don't build assembly dos programs after I discover MASM32 SDK, because I don´t have that tools in this machine. I still keep the old machine, but I don't know where is hard disk    

[Gunther]

HSE,

Attached EXE. Evidently I don't build assembly dos programs after I discover MASM32 SDK, because I don´t have that tools in this machine. I still keep the old machine, but I don't know where is hard disk    

That's all right. Please don't bother about the missing old hard disk with the tools.

[FORTRANS]

Hi,

   I also just ran the EXE included.  What version of MASM is required?

   Anyway, here are the results from running in a VDM with a rather old
system.

Code Select Expand

                         System and Memory Information:
                         ==============================
                                                                               
Start Address 16 Bit Code                             = 78672                   
Start Address 32 Bit Code                             = 82304                   
Start Address private data for DPMI Host              = 88768                   
Start Address DOS buffer                              = 89808                   
DOS buffer length in byte                             = 562480                 
Largest available free Extended Memory Block in bytes = 16777216               
First free address above 1 MB                         = 4194304                 
Last free address above 1 MB                          = 20971520               
                                                                               
Filling an array in the Extended Memory with values.                           
Done.                                                                           
                                                                               
Reading these values back: 14680060                                             
Done.                                                                           
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
Press any key to end the application...                                         


Regards,

Steve N.

[Gunther]

Steve,

thank you for your test results.

What version of MASM is required?

That's a good question. The decisive factor is probably the corresponding linker. Here is the rough logic of the program: It starts as Real Mode application and ends
as a 16-bit Protected Mode program. In the meantime, however, it's switched to 32-bit protected mode and should be able to use the entire address space linearly.
This all happens in PMSHELL.ASM. The source code is well commented and you can find all the details there. The trick now is that the program contains a 16-bit and
a 32-bit segment. So the linker must be able to link both segments properly. TLINK does this without complaint. Whether the 16-bit linker from MS can do this would
have to be tried.

Which VDM did you use?

[FORTRANS]

Hi,

Which VDM did you use?

   OS/2 version 4.

Cheers,

Steve N.

[Gunther]

Steve,

   OS/2 version 4.

that's not surprising. OS/2 has always had a very solid DOS emulation. I'm thinking of setting up Warp 4 as a virtual machine. JWASM has an OS/2 version.
Earlier there was also a GCC for OS/2 maintained by Eberhard Mattes. I don't know what the situation is like today.

[FORTRANS]

Hi Gunther,

What version of MASM is required?

That's a good question. The decisive factor is probably the corresponding linker.

   Actually, a linker I have works, and my MASM setup for DOS is too old.
The linker linked the two object modules in your zip file to an EXE that
worked.  Though it was four bytes different in size.

Code Select Expand

Microsoft (R) Segmented-Executable Linker  Version 5.15
Copyright (C) Microsoft Corp 1984-1991.  All rights reserved.

Usage:

LINK
LINK @<response file>
LINK <objs>,<exefile>,<mapfile>,<libs>,<deffile>

Valid options are:
  /?                             /ALIGNMENT
  /BATCH                         /CODEVIEW
  /CPARMAXALLOC                  /DOSSEG
  /DSALLOCATE                    /EXEPACK
  /FARCALLTRANSLATION            /HELP
  /HIGH                          /INCREMENTAL
  /INFORMATION                   /LINENUMBERS
  /MAP                           /NODEFAULTLIBRARYSEARCH
  /NOEXTDICTIONARY               /NOFARCALLTRANSLATION
  /NOGROUPASSOCIATION            /NOIGNORECASE
  /NOLOGO                        /NONULLSDOSSEG
  /NOPACKCODE                    /OVERLAYINTERRUPT
  /PACKCODE                      /PACKDATA
  /PADCODE                       /PADDATA
  /PAUSE                         /PMTYPE
  /QUICKLIBRARY                  /SEGMENTS
  /STACK                         /TINY
  /WARNFIXUP

   As far as GCC, there is something on the Hobbes OS/2 repository.
Though it looks a bit skimpy.

Regards,

Steve

[Gunther]

Steve,

it is a bit cumbersome, but the following way works: I have assembled both files with the MASM from the MASM32 package.

Code Select Expand


e:\masm32\work>\masm32\bin\ml /c PMSHELL.ASM
Microsoft (R) Macro Assembler Version 6.14.8444
Copyright (C) Microsoft Corp 1981-1997.  All rights reserved.

Assembling: PMSHELL.ASM

e:\masm32\work>\masm32\bin\ml /c examp1.asm
Microsoft (R) Macro Assembler Version 6.14.8444
Copyright (C) Microsoft Corp 1981-1997.  All rights reserved.

Assembling: examp1.asm


TLINK then linked the resulting OBJ files without complaint. The resulting EXE files are different in size but have the same functionality.

   As far as GCC, there is something on the Hobbes OS/2 repository.
Though it looks a bit skimpy.

I'll take a look at it.

[_japheth]

The new machine only allows 1.2 GB. This will be sufficient in most cases. But what is the cause of this behavior?

Huge parts of physical memory might be mapped beyond the 4 GB barrier. The highest address 4FFFFFFF showed by xmsstat might suggest that only 1.25 GB are mapped below 4 GB.

BIOS function int 15h, ax=E820h is the method to get the system's memory map. tool memstat in https://github.com/Baron-von-Riedesel/Jemm/releases/download/v5.80/JemmB_v580.zip uses that call.

Usually there were at least 3 GB below 4 GB, but with 64-bit systems being now the standard that may have changed. Also, the PCIe graphics card may reserve quite some address space below 4 GB to map its video ram there.

[Gunther]

Andreas, thank you for your fast answer.

Usually there were at least 3 GB below 4 GB, but with 64-bit systems being now the standard that may have changed. Also, the PCIe graphics card may reserve quite some address space below 4 GB to map its video ram there.

This could be the cause. Here is the result of MEMSTAT:

Code Select Expand


conventional memory (Int 12h): 629 kB
XBDA at segment 9d40, size 11 kB
Int 15h, ah=88h, extended memory: 0 kB
Int 15h, ax=E801h failed
Int 15h, eax=E820h:
address range          size       type
----------------------------------------------------
000000000-00009d3ff      9d400  1 (available)
00009d400-00009ffff       2c00  2 (reserved)
0000e0000-0000fffff      20000  2 (reserved)
000100000-035419fff   3531a000  1 (available)
03541a000-03779cfff    2383000  2 (reserved)
03779d000-037826fff      8a000  3 (ACPI reclaimable)
037827000-0388a7fff    1081000  4 (ACPI NVS)
0388a8000-03a316fff    1a6f000  2 (reserved)
03a317000-04fffffff   15ce9000  1 (available)
100000000-89fffffff  7a0000000  1 (available)
050000000-06fffffff   20000000  2 (reserved)
0fe000000-0fe010fff      11000  2 (reserved)
0fec00000-0fec00fff       1000  2 (reserved)
0fed00000-0fed00fff       1000  2 (reserved)
0fee00000-0fee00fff       1000  2 (reserved)
0ff000000-0ffffffff    1000000  2 (reserved)
----------------------------------------------------
available: 32432 MB, ACPI: 17452 kB, rsvd: 590 MB, total: 33039 MB


ACPI eats up a lot of memory.

Probably I have to switch to the BIOS interrupt 15h after all.

[_japheth]

Probably I have to switch to the BIOS interrupt 15h after all.

That depends what you want to achieve. Accessing memory beyond the 4 GB barrier requires some low-level work for a DOS app, since there exists no "unreal"-mode trick to do that.