Date: Sat, 22 Nov 1997 20:39:46 -0500 (EST) From: Chuck Robey <chuckr@glue.umd.edu> To: Charles Mott <cmott@srv.net> Cc: chat@FreeBSD.ORG Subject: Re: FreeBSD Book Club Message-ID: <Pine.BSF.3.96.971122203236.14432Z-100000@picnic.mat.net> In-Reply-To: <Pine.BSF.3.96.971122162849.7232A-100000@darkstar.home>
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On Sat, 22 Nov 1997, Charles Mott wrote: > > Yeah, I wasn't calling the world's greatest book, but when the field is > > that thin, well, I think it has to be a keeper, else you get nothing at > > all. The van Gilluwe book disappointed me in skipping many things I was > > specifically interested in, while doing a pedagogical OS for a class, but > > I had the field pretty well covered. When you leave the Unix and Windows > > fields, what's left is either completely roll-your-own, or you have to get > > really familiar with DPMI, and there's just nothing on DPMI out there > > except raw specs. Luckily, it's not the worst spec in the world. > > You've won the argument and saved the day for Shanley. I won't be testing > amazon.com's return policy. At the risk of me sounding a little ignorant > here, what is DPMI? I had to learn about it, doing the OS that had to run under a Win95 dos box. In case you're wondering about that, it wasn't my idea ... anyhow, DPMI is a dos-world memory manager, one of basically 3 standards that exist. The lowest level is the extended memory standard, XMS. The next level up is VPCI, but VPCI didn't allow for multiple processes very well, and isn't therefore terribly useful. DPMI is represented by two specs, one for level 0.9 (which has by far the best writeup) and 1.0. Because the docs are so much better for 0.9, there are a whole field of DPMI servers available, that are mostly 0.9+ things. Allows you to do things like memory map areas, have demand loaded areas, do a malloc that is protected from other processes and returns larger than 64K, get/set/mangle and otherwise contort various descriptors, there's a lot of functionality. If you're doing things in the dos world, and don't want to depend on Windows libs, DPMI is the spec to use. There's a GNU version also. If you want to know more, there's a protected mode mailling list that has a pretty good signal/noise ratio. Send me mail if you're interested. > > Charles Mott > > > ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@glue.umd.edu | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+-----------------------------------------------
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