Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!crdgw1!uunet!cme!durer.cme.nist.gov!przemek From: przemek@rrdstrad.nist.gov (Przemek Klosowski) Newsgroups: comp.arch Subject: Re: Segmented Architectures ( formerly Re: 48-bit computers) Message-ID: Date: 5 Apr 91 16:09:07 GMT References: <23615@as0c.sei.cmu.edu> <1991Apr04.202446.13595@kithrup.COM> <23660@as0c.sei.cmu.edu> <1991Apr05.010343.16664@kithrup.COM> Sender: news@cme.nist.gov Organization: U. Notre Dame/NIST Lines: 43 In-reply-to: sef@kithrup.COM's message of 5 Apr 91 01:03:43 GMT >>>>> On 5 Apr 91 01:03:43 GMT, sef@kithrup.COM (Sean Eric Fagan) said: Bob> In <23660@as0c.sei.cmu.edu> firth@sei.cmu.edu (Robert Firth) writes: ... 50000x50000 array of doubles... Sean>Gee, this works on current 32-bit machines? Bob> No. But you claimed to have a machine with 32-bit integer and 48-bit Bob> addressing, and challenged us to produce code that ought to work on Bob> such a machine but won't on yours. The above was my response. Sean> Which was incorrect. I impose the limitation, as I said in my first Sean> article that no single object (such as your array) be larger than 4GB. Sean> Now, please show me how my proposed segmented machine a) breaks existing Sean> *correct* code, and/or b) makes things difficult or impossible? Yes, Sean> *You* are the one who's pathetic, buddy. Hey, hey, a little bit worked up, aren't we? Sean seems to believe that since all code (most of it, anyway) has a 4GB limitation currently, all code adressing anything above that is broken. So what is the point of providing 48 bytes of address then? I would think that since it is there, it should be used. Bob gave a valid example of the program that uses the capability that _would_ be provided by the 48 bit flat adressing. If it worries Sean that this is unportable to VAX, please consider that in reality one would have to parametrize the size of the table anyway, since even though e.g. VAX has the 32 bit address space, the different operating systems put a practical limit on the working set sizes etc. forcing one to limit the size of a problem to smaller values. And it of course isn't just a fancy to try to squeeze a bigger array. In the area I am somewhat familiar with, physical modelling, 4 GB of memory allows to model a very modest 640x640x640 system of Heisenberg (vector) spins, since each spin is a pair of double-precision values. >>>We need those address bits!<<< Let me just say that I wish that people would just take a good counter-argument and not cover the confusion with panache. -- przemek klosowski (przemek@ndcvx.cc.nd.edu) Physics Department University of Notre Dame IN 46556