Re: [Freedos-user] How to set CWSDPMI for 4GB of RAM?

[Florian Xaver]

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Hi!
| Are you using a XMS driver (probably), and which one
| (HIMEM.SYS/HIMEM.EXE/FDXMS.SYS/FDXXMS.SYS) exactly?
| can you run MEM /C /P from the commandline and paste the output into
| your next email? That way you can see how much RAM the XMS driver gives
| access to.
| I don't know if XMS driver is required for CWSDPMI though.
| Bernd
XMS driver isn't required. I don't know the answer, but you should
also post your question in the DJGPP newsgroup!
Bye, Flo
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[Freedos-user] DPMI with 4 GB

[Roberto Waldteufel]

Hi All,
 
No I am not using Himem.Sys or Himem.exe. I am 
writing for 32-bit protected mode, so I need DPMI for the flat memory model, 
which in theory should enable the use of all 4 GB of RAM on my system, not just 
extra high memory in the real mode. No such real mode high memory manager is 
needed under CWSDPMI. 
 
I don't think the motherboard is the cause of the 
trouble - I had this computer custom built by Dell with 4 x 1 GB chips. It came 
with Windows XP (Home) preinstalled, which demands over 2 GB just for Windows, 
leaving my applications only about 1.75 GB to use, which is my main reason for 
wanting to write for the DOS platform so as to have all of the 4 GB available, 
but the CWSDPMI server only seems to recognise 2 
GB, which is at least a small improvement over Windows as I gain about about 250 
MB extra RAM. However, Windows is so bloated it actually uses the other 2.25 GB 
of RAM, whereas Freedos is nice and lean and doesn't need such an excessive 
amount of memory for its own use - it's just that the DPMI server doesn't see 
more than 2 GB of physical RAM. However, the fact that Windows can access the 
remaining RAM for its own use proves that the motherboard must be able to cope 
with the full 4 GB of physical RAM.
 
Yes I did try DPMIONE (for which high end real mode 
memory IS needed - I used the himem.sys file to load himem.exe and emm386 for 
this) instead of CWSDPMI but I found this even worse, with only 64 MB of 
RAM visible to my applications under this DPMI server! I have not tried DOS32A 
yet, but will look into this. 
 
Best Wishes,
 
Roberto

Re: [Freedos-user] DPMI with 4 GB

[Michael Devore]

At 01:11 PM 4/15/2005 +0100, Roberto Waldteufel wrote:
Hi All,
No I am not using Himem.Sys or Himem.exe. I am writing for 32-bit 
protected mode, so I need DPMI for the flat memory model, which in theory 
should enable the use of all 4 GB of RAM on my system, not just extra high 
memory in the real mode. No such real mode high memory manager is needed 
under CWSDPMI.
You have an insufficient number of data points to draw detailed 
conclusions.  Try loading FreeDOS HIMEM.EXE, and then run latest MEM.EXE to 
see how much XMS is available.   Also if, as you seem to indicate, you have 
HIMEM.SYS from a late version MS-DOS available, load that HIMEM.SYS instead 
of HIMEM.EXE, then run MEM.EXE to see how much XMS is available under it.

The values reported may demonstrate whether anything sees the full 4G under 
standard BIOS calls.


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[Freedos-user] DPMI 4 GB problem - EMM386 sees 3.24 GB but CWSDPMI sees only 2 GB

[Roberto Waldteufel]

Hi everyone,
 
Further to my last message, I tried a memory dump 
in 16 bit real mode running himem.exe and emm386 and found a great improvement 
compared to 32-bit protected mode using CWSDPMI (or DPMIONE which was even 
worse). A total of 3.24 GB of extended RAM is detected - here is the 
output:-
 
Memory 
Type   
Total  -  
Used = Free 
(largest)
------    
-   

Conventional 
640K    
74.2K    565K 

Upper 
(XMS) 
64.0K
Extended (INT15)  
3.24G    
0
Extended 
(XMS16) 
63.9M
Extended 
(XMS32) 
3.21G
Expanded (EMS)   
32.1M  
64K   
32.0M
-
FreeDOS is resident in low memory.
 
This seems to confirm that the 4 GB of 
physical RAM is visible to the XMS memory manager in real mode, even if 
about 750MB or so is unaccounted for - it is still a vast improvement on 
protected mode using a DPMI server with just under 2 GB via CWSDPMI, 
1.75GB via Windows XP DPMI server, or 65MB via DPMIONE. 

 
Incidentally, this usage of himem.exe and 
emm386.exe prevents CWDPMI from switching to 32-bit protected mode. However, 
with DPMIONE it is the other way around - DPMIONE needs to have himem.exe and 
emm386.exe to work at all. I am not sure, but if I remember correctly doesn't 
EMM386 use VCPI rather than DPMI? I think DPMIONE just acts as an interface 
between VCPI and an application requesting DPMI, which would explain why it 
needs to have EMM386 running to provide the VCPI services. It would be ironic if 
the only way to access the bulk of my 4GB RAM is to run in 16 bit 
mode!
 
Thanks to all for your suggestions,
 
Roberto

Re: [Freedos-user] DPMI with 4 GB

[Bernd Blaauw]

There is such a thing as I/O mapping, which decreases the amount of 
usable RAM. Usually the memory is mapped to just below 4GB.
AGP GART is there for example (256MB usually), as well as other things 
(PCI for example).
Thus, you usually see 3.3 up to 3.5GB of RAM.

Bernd
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