From: Nate Eldredge Newsgroups: comp.os.msdos.djgpp Subject: Re: far pointers again Date: Thu, 07 Oct 1999 13:32:24 -0700 Organization: Harvey Mudd College Lines: 32 Message-ID: <37FD0358.68F04540@hmc.edu> References: <7tho7c$p4i AT cs DOT vu DOT nl> NNTP-Posting-Host: mercury.st.hmc.edu Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: nntp1.interworld.net 939328383 74119 134.173.45.219 (7 Oct 1999 20:33:03 GMT) X-Complaints-To: usenet AT nntp1 DOT interworld DOT net NNTP-Posting-Date: 7 Oct 1999 20:33:03 GMT X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.2.13pre12 i586) X-Accept-Language: en To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Reply-To: djgpp AT delorie DOT com Fokkema, DBRA, 1043730 wrote: > I understand all this, but I thought it was nice if you could access all > memory available. But if gnu cc doesn't support far pointers, and it is, > as was suggested to me, just a flitch in the early intel processors, does > this mean that dos c compilers are about the only ones that implement far > pointers which they invented themselves (i.e. it is not part of the ansi-c > standard)? That's correct. > : I wouldn't support it because I think there are other, better ways to > : do things (quite apart from anything else, code that was written for > : a segmented memory model is 100% ugly to port to any other hardware, > : wheras if you are writing an OS, you can get all the same protection > : benefits from paging systems which work a similar way on all hardware). > > How exactly do I get the same protection? By paging out all the memory > belonging to other processes? How many platforms (and which) do support > segmented memory models? I understand from your '100% ugly to port' statement > that this aren't many. Typically you have a separate set of page tables for each process, in which only the pages belonging to that process are mapped. And yes, there are very few other architectures that use a segmented memory model. In fact, I can't think of any others. -- Nate Eldredge neldredge AT hmc DOT edu