Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!cambridge.apple.com!bill From: bill@cambridge.apple.com (Bill St. Clair) Newsgroups: comp.sys.mac Subject: Re: IIci vs. IIcx - Virtual Memory Message-ID: Date: 5 May 90 18:25:44 GMT References: <8904@hydra.gatech.EDU> <20652@eagle.wesleyan.edu> Sender: news@cambridge.apple.com Distribution: usa Organization: Apple Computer Inc, Cambridge, MA Lines: 67 In-reply-to: bparsia@eagle.wesleyan.edu's message of 3 May 90 17:50:11 GMT From: bparsia@eagle.wesleyan.edu Newsgroups: comp.sys.mac Date: 3 May 90 17:50:11 GMT Distribution: usa In article <8904@hydra.gatech.EDU>, gt4586c@prism.gatech.EDU (WILLETT,THOMAS CARTER) writes: [stuff deleted...] I believe that this is incorrect. The "14-1 per slot" rule is for Connectix' Virtual, not for system 7.0. 7.0 should let you access as much memory as you have disk space with *any* 68030 (or 68020 + a PMMU). As sys 7.0 is currently non-existing, the only way to get virtual memory is with Virtual. Not entirely true. System 7.0's virtual memory will have the same limitation ("14-1 per slot") as Virtual unless you have 32-bit clean ROMs (standard on the IIci & IIfx). The 32-bit clean ROMs will work in the IIcx, but you'll have to buy and install them (they come on a SIMM, but I know nothing about their where to buy them). The IIci *can* potentially have more VM than the IIcx, if one uses the on board video circutry rather than a NuBus video card. If VM is all one wants at the moment, I don't think that the extra megabyte is worth the cost differential. True. However, I'm confused. I thought that the Mac OS currently supports *only* 8 megs of memory. Does Virtual patch this in some manner? The limitation is that the ROM is expected to be at address 800000 hex (8 Megs). Virtual fools the finder into thinking that there is an application sitting in memory where the ROM is (or something like that). Thus your virtual address space is split up into an 8 Meg chunk and a "6 meg - 1 meg per filled NuBus slot" chunk. In any case, with system 7.0, all restrictions on memory will be for all intents and purposes lifted (with the advent of 32-bit memory addresses). And the Mac will be able to thrash almost like a real operating system. I don't know what > hardware differences exist that allow the IIci and IIfx to do better > than the other macs. No hardware differences, just the 32-bit clean ROMs. As far as virtual memory is concerned, there are none. The PMMU is all you need, and with the '030, it's what you get. Does anyone know if the limitations for > Connectix' Virtual are the same? Let me know if I have erred. I wish someone official like from Apple would post a full, clarificatory article on this topic, as I have seen *alot* of misinformation flying about (of which my current posting may be one). I work for Apple, but I'm no official, so I include the standard disclaimer that all my musings are my own opinions, not my employer's. Bill St. Clair bill@cambridge.apple.com