From:	Charles Sandmann <sandmann AT clio DOT rice DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Accessing 4GB w/o DPMI
Date:	Mon, 19 Aug 2002 23:45:05 CDT
Organization:	Rice University, Houston TX
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> Can I write a program in DJGPP that will allow me to access all
> physical memory in a machine (up to 4GB) w/o having to resort to
> loading some sort of DPMI driver?  

Yes - you can write the program with the DJGPP tools (GCC compiler).
You would need to write your own stub loader to switch to protected
mode, manage hardware interrupts, manage DOS/BIOS calls.  This is
not a trivial task.  Since DPMI drivers are small and can be bypassed,
there's not a real reason to avoid them, however.

> I'd like to be able to boot from a
> DOS disk, and access huge amounts of RAM w/o much more functionality
> than the peeking and poking I once did in BASIC programs.

While I haven't tried it, I don't know why you wouldn't be able to 
access all 4Gb physical memory in a machine with the PMODE DPMI
provider.  It does not turn on paging if VCPI isn't present, so all
memory is mapped one-to-one - and a simple farpeek or farpoke could
get to it all.

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