Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!snorkelwacker!bloom-beacon!bu.edu!mirror!frog!cpoint!jjmhome!m2c!umvlsi!dime!dime.cs.umass.edu!moss From: moss@ibis.cs.umass.edu (Eliot Moss) Newsgroups: comp.arch Subject: Re: Capabilities and Object Oriented Programming Message-ID: Date: 20 Mar 90 19:54:00 GMT References: : <45425@ames.arc.nasa.gov> Sender: news@dime.cs.umass.edu Reply-To: Moss@cs.umass.edu Organization: Dept of Comp and Info Sci, Univ of Mass (Amherst) Lines: 24 In-reply-to: lamaster@ames.arc.nasa.gov's message of 20 Mar 90 02:07:29 GMT I don't think you would use traditional page oriented schemes for "system level objects", because the average object is much too small. For example, Smalltalk objects average about 40 bytes. It is a real challenge to design systems that do not swamp this with space and time overheads. The usual approach is to use segments rather than pages (though one can and probably should store segments within pages (or some large unit of memory) for backing store purposes). This tends to suggest that the best support requires a rather different hardware approach, assuming you want all the checks in hardware. If you're willing to let the compiler/run-time system do some of the work (consistent with some notions of the RISC philosophy) then you could use a more conventional architecture ... *but* your language must be a safe language or the safety of the whole thing falls apart. This means C is right out, unless protection, etc., is not an issue (many PC class systems ignore protection and seem to get by all right, probably because most people run little other than reasonably well debugged, commercially available programs). Well, that's all I have time for .... Eliot -- J. Eliot B. Moss, Assistant Professor Department of Computer and Information Science Lederle Graduate Research Center University of Massachusetts Amherst, MA 01003 (413) 545-4206; Moss@cs.umass.edu