From: Charles Sandmann 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 Lines: 19 Message-ID: <3d61c951.sandmann@clio.rice.edu> References: <2c6a63a7 DOT 0208192030 DOT f501db4 AT posting DOT google DOT com> NNTP-Posting-Host: clio.rice.edu X-Trace: joe.rice.edu 1029819205 3009 128.42.105.3 (20 Aug 2002 04:53:25 GMT) X-Complaints-To: abuse AT rice DOT edu NNTP-Posting-Date: 20 Aug 2002 04:53:25 GMT X-NewsEditor: ED-1.5.9 To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Reply-To: djgpp AT delorie DOT com > 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.