Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!cs.utexas.edu!usc!rpi!fargo From: fargo@iear.arts.rpi.edu (Irwin M. Fargo) Newsgroups: comp.arch Subject: Re: Segmented Architectures ( formerly Re: 48-bit computers) Message-ID: Date: 8 Apr 91 15:43:26 GMT References: <1991Apr06.030330.1533@kithrup.COM> <572@lysator.liu.se> Organization: Fargo HQ, Inc. Lines: 35 Nntp-Posting-Host: iear.arts.rpi.edu In article <572@lysator.liu.se> bellman@lysator.liu.se (Thomas Bellman) writes: > > [a few paragraphs removed] > >Sometimes you don't want the segmentation. Sometimes you want the >flat address modell. This is equivalent to accessing the physical >disk in a file system. The file system it self want to do this, but >will probably not want to let the user do that himself. Same for >memory, the OS wants to address the memory as a flat space, but might >not want the user programs to do this. > With what I know of OSs, wouldn't segmentation be what the OS wants? In most of today's computer systems, virtual memory is the Big Thing (tm). The idea behind virtual memory (correct me if I'm wrong), is that a program can read/write to memory as if memory were directly connected, but it is actually re-mapped to a previously specified location in physical memory. Obviously, virtual memory mappers of today use pages to allow more flexible ways of memory mapping. Couldn't a virtual memory page be considered the same as a segment? (a la the Intel 80386 in protected mode) If the OS (or any other program really wants, you can tell the MMU you want one page that takes up all of memory of lots of little pages. My whole point is, if we consider virtual memory pages to be equivalent to segments, then it would seem that quite a few systems do use segmentation and that it really is not that outdated an idea. -- Thank you and happy hunting! Actually: Ethan M. Young Internet: fargo@iear.arts.rpi.edu Please press 1 on your touch tone Bitnet (??): userfp9m@rpitsmts.bitnet phone to speak to God... Disclaimer: Who said what?