Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!batcomputer!cornell!uw-beaver!zephyr.ens.tek.com!tektronix!sequent!dafuller From: dafuller@sequent.UUCP (David Fuller) Newsgroups: comp.arch Subject: Re: Segmented Architectures ( formerly Re: 48-bit computers) Message-ID: <56399@sequent.UUCP> Date: 28 Mar 91 22:48:14 GMT References: <1991Mar21.164242.886@sj.nec.com> <23189@as0c.sei.cmu.edu> Reply-To: dafuller@sequent.UUCP (David Fuller) Organization: Sequent Computer Systems, Inc Lines: 43 In article <23189@as0c.sei.cmu.edu> firth@sei.cmu.edu (Robert Firth) writes: >In article efeustel@prime.com (Ed Feustel) writes: > >>The major difficulty with a segmented architecture in today's marketplace >>arises from the use of the language C and C's notion of a pointer as the >>total address. > >No. The major difficulty with a segmented architecture is that it's >wrong, and the von-Neumann model is right. This is not a language >issue. One of the most fundamental, and most pervasive, idioms in >practical computing is the mapping function whose domain is a >subset of the natural numbers, in other words > > array (0..max) of Object > I would tend to ally with Ed Fuestel here; if you look at the 8086 scheme it fits really well for Pascal: 4 segments, one each for code, data, heap and stack. The Pascal runtime system insulates you from the details of the machine but there's no reason you can't have arbitrary-sized arrays as long as you use the runtime's idioms. If you insist on manipulating machine-level structures as pointers (an idea that still makes me queasy) then you get what you deserve (recalling the DG port I did where the hibit indicated a "char" pointer *shiver*). C is a lousy fit on segmented architectures. I hope never to code another FAR pointer as long as I live. I hope also that previous work done on 286 Xenix remains unbuggy forever. I would also question whether "unsegmented" is a necessary feature of Von Neumann architectures. Respectfully, Dave -- Dave Fuller Sequent Computer Systems Think of this as the hyper-signature. (708) 318-0050 (humans) It means all things to all people. dafuller@sequent.com