Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!unmvax!uokmax!servalan!epmooch!ben From: ben@epmooch.UUCP (Rev. Ben A. Mesander) Newsgroups: comp.sys.amiga.hardware Subject: Re: Amiga Custom Chips - Mem management and resource tracking Message-ID: Date: 3 Apr 91 23:45:45 GMT References: <1991Apr2.235710.13984@news.iastate.edu> <1991Apr3.201259.8377@engin.umich.edu> <1991Apr3.153236.1@vf.jsc.nasa.gov> <1991Apr4.034655.3681@uniwa.uwa.oz> Distribution: world Lines: 23 >In article <1991Apr4.034655.3681@uniwa.uwa.oz> andreww@uniwa.uwa.oz (Andrew John Williams) writes: >Something I've always wanted to know - if the problem of no MMU in the >Amiga is because the messages need shared memory, why not make just that >little bit of memory common to any tasks that want it. The rest can be >protected. Add some new calls (or flags) to the OS for requesting >protected memory or message memory. The old software can call the old >routines and get unprotected memory - no change for them. Any new >software can use the new calls. The new software will be more robust, >and thus more popular, so eventually there will be almost no old >software in use. And there's no problem with machines like the 500 with >no MMU - if they ask for protected memory, give them unprotected and >tell them its not. The program won't care - it will just crash worse if >something goes wrong. Which is what we've got now. >So someone tell me where I've gone wrong in my thinking Well, for one thing, the messages can contain pointers to other blocks of memory, rather than the entire message. So that would break your proposed scheme. -- | ben@epmooch.UUCP (Ben Mesander) | "Cash is more important than | | ben%servalan.UUCP@uokmax.ecn.uoknor.edu | your mother." - Al Shugart, | | !chinet!uokmax!servalan!epmooch!ben | CEO, Seagate Technologies |