DJGPP FAQ -- Memory allocation peculiarities under Windows 9X

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15.6 Memory allocation peculiarities under Windows 9X

Q: I seem to be unable to get more than 16 MBytes of virtual memory under Windows 9X, even though I have 32 MBytes of RAM installed on my machine, and a lot of disk space...

A: You must set the maximum amount of DPMI memory to 65535K in the DOS applications' Property Sheets. Click on the Properties button of the DOS box toolbar, then click on the Memory tab, and type the number 65535 in the box under DOS Protected Mode Memory. If you leave that setting at the default "Auto", your programs are at Windows' mercy, and in many cases will get only 16 MBytes. You must actually type 65535 inside the dialog box, as checking out the values from the list Windows offers will never get you past 16384 (i.e., 16MB).

If you have more than 64MB of physical memory installed, you can specify the amount of memory on the EMM386 command line in your CONFIG.SYS, like this:

      DEVICE=C:\WINDOWS\EMM386.EXE NOEMS L=131072

I'm told that this line (here for 128MB of installed memory) together with an "Auto" setting of the DPMI memory for the DOS box allows DJGPP programs to use up to 117MB of memory when running from the DOS box under Windows 9X.

Note that you cannot allocate more than half the available memory in one chunk under Windows 9X, exactly as the things are under Windows3.X, and you cannot have more than 64 MBytes of virtual memory available to DJGPP programs running on Windows, unless you have more than 64MB physical memory installed.

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