Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!snorkelwacker.mit.edu!bloom-picayune.mit.edu!athena.mit.edu!jfc From: jfc@athena.mit.edu (John F Carr) Newsgroups: comp.arch Subject: Re: Segmented Architectures ( formerly Re: 48-bit computers) Message-ID: <1991Apr6.211320.18594@athena.mit.edu> Date: 6 Apr 91 21:13:20 GMT References: <1991Apr04.023845.3501@kithrup.COM> <1991Apr04.230953.15294@kithrup.COM> Sender: news@athena.mit.edu (News system) Organization: Massachusetts Institute of Technology Lines: 17 In article peter@ficc.ferranti.com (Peter da Silva) writes: >No, I didn't miss the point. If I have a 48 bit wide VM address and can't >operate on any object larger than a 32 bit wide pointer can address, then >it's a problem. Why do you care what the address size is? A programmer's concern should be: how many objects can I have, how big can each be, and how fast does the code run? Let the system designers decide whether to have a flat address space or segments. If you have code which requires 2^40 byte objects, put this in your requirements when you buy a system. The cost of 2^40 bytes of memory can finance the OS and compiler changes needed to support such objects on a segmented MMU. -- John Carr (jfc@athena.mit.edu)