From: Shawn Hargreaves Newsgroups: comp.os.msdos.djgpp Subject: Re: Physical memory, virtual memory. DJGPP+CWSDPMI, how they work? Date: Sun, 1 Feb 1998 19:20:06 +0000 Organization: None Distribution: world Message-ID: <75hd6DAmrM10EwlZ@talula.demon.co.uk> References: NNTP-Posting-Host: talula.demon.co.uk MIME-Version: 1.0 Lines: 37 To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Precedence: bulk Eli Zaretskii writes: >This is not entirely accurate. There *is* a bit in the selector >descriptor which says whether the segment is code or data. True, but that doesn't help with a djgpp program where the code and data segments both cover the entire address space of your program! A DPMI implementation that tried to make paging decisions based on these flags would come up with random results depending on which selector it looked at first, and even if it could work out which part of memory contained your code, it still has no way of knowing what file the data came from. >However, note that this method has its drawbacks. For example, you >cannot write into a running executable's .exe file on such systems. That can indeed be annoying. When using MSVC, my compiles frequently fail at the link phase because I forget to quit out of the program instance that I was previously testing :-) >I think with DPMI 1.0, you can. Too bad it is only supported by a >single DPMI server. The problem is that even if someone spent the time to upgrade CWSDPMI to a full DPMI 1.0 implementation, it would be pretty much useless because we still wouldn't have these features under win95, and I don't think many people these days are willing to write programs that will only work in a clean DOS environment! What do you think it would it take to make Microsoft start supporting DPMI 1.0? It is ridiculous that they are still only using version 0.9 of an official standard like this, especially since the real thing offers so many major improvements, but I find it hard to imagine them taking much notice of our complaints :-) -- Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/ "Pigs use it for a tambourine" - Frank Zappa