Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!cbmvax!daveh From: daveh@cbmvax.UUCP (Dave Haynie) Newsgroups: comp.sys.amiga Subject: Re: Memory Management Message-ID: <2868@cbmvax.UUCP> Date: Wed, 25-Nov-87 13:39:01 EST Article-I.D.: cbmvax.2868 Posted: Wed Nov 25 13:39:01 1987 Date-Received: Sun, 29-Nov-87 01:20:53 EST References: <7958@steinmetz.steinmetz.UUCP> Organization: Commodore Technology, West Chester, PA Lines: 52 in article <7958@steinmetz.steinmetz.UUCP>, oconnor@sunray.steinmetz (Dennis Oconnor) says: > In article <...> klm@atkins.UUCP (Kevin [...] McBride) writes: >>In article <...> dillon@CORY.BERKELEY.EDU (Matt Dillon) writes: >>> Virtual memory != EachTaskGetsItsOwnAddressSpace >>> As far as the Amiga goes, the only compatible solution is a Linear >>>virtual address space over the entire system. >> >>This seems like a perfectly rational and compatible way of doing VM on >>the Amiga. >>I like it! I like it! I wish I had thought of it! > > Well, on the one hand, this means you are still limited to 8.5MB of > memory. Doesn't it? Of course not! The limits you see are based on the 68000 memory map. There's 8.5M - 64K of autoconfigure space; leaving the .5M - 64K for I/O, that gives you the popular 8 megs. Now add the basic 512K of CHIP RAM, and you're up to your 8.5 meg. The A2000 and A500 have an additional 512K of RAM at $C00000, for a total of 9 megs of real memory. Now if you wanted to talk in theoretical maximums for the 68000 based machine, there's another 1.5 meg of space allocated to CHIP RAM, for a total of 10.5 meg given an as-yet non-existant Agnus to address that 2 meg. Then there's an addition 1.25 meg in the $C00000 area, for a total of 11.75 meg that can be addressed by a 68000 based machine. But that's for a 68000 based machine. Anything with an MMU probably has a 68020 attached. That adds an additional 4 gigabytes - 16 megs of address space. I don't forsee anyone hooking up a gig or two of real memory in the next year. > So why bother? Just buy the 8MB and have real speed. > What does 8MB cost, anyway? $1500 ? Given the above linear address model, which is certainly the one that makes sense under AmigaOS, you have a virtual memory handler. If you don't want to use it, don't. If you do, you probably have something in your startup sequence that does: AddVMem 20M SWAP: Or something along those lines. That adds 20M of virtual memory to the free memory list, links a SWAP: device like a hard disk to your page fault server, and you're all done. If you have 8 megs of real memory on top of that, and only use 6meg, you never get a fault, and you never page. If you use 15 megs, though, instead of dying in flames, you get to run, only slower. > Dennis O'Connor oconnor@sungoddess.steinmetz.UUCP ?? -- Dave Haynie Commodore-Amiga Usenet: {ihnp4|uunet|rutgers}!cbmvax!daveh "The B2000 Guy" PLINK : D-DAVE H BIX : hazy "I can't relax, 'cause I'm a Boinger!"