Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!swrinde!zaphod.mps.ohio-state.edu!rpi!floyd From: floyd@pawl.rpi.edu (Patrick J Wetmore) Newsgroups: comp.sys.apple2 Subject: Re: Multitasking on a II Message-ID: Date: 15 Dec 90 00:24:02 GMT References: <10063@darkstar.ucsc.edu> <7TF^W^=@rpi.edu> <90348.145140AABENSON@MTUS5.BITNET> Organization: Rensselaer Polytechnic Institute, Troy NY Lines: 50 Nntp-Posting-Host: pawl18.pawl.rpi.edu In article <90348.145140AABENSON@MTUS5.BITNET> writes: >Hey Pat! Listen up! I did. And was unimpressed. >An IBM PC is somewhat lower on the power scale than a IIgs. A IIgs DOES >have this thing called a "Memory Manager". You see, what it does is it >allocates pieces of memory for whoever asks for it. The reason for this is Thank you very much, I know about it. However, an MMU prevents you from zapping memory that has been allocated to another process. If you are programming, and have a teensy little bug that curdles a pointer (this happens to ANYONE who programs in C. It's part of a process called debugging. If you're a programmer who's never gotten a coredump, well, then, my hat's off to you.) then you will overwrite another processes memory, on the IIGS and other machines without an MMU. Yes, you can get along fine multi- tasking without an MMU, as long as your software has not a single bug in it. An error in one process is likely to hammer the machine badly, and crash it, without an MMU - it's not that hard to send a pointer into the OS's space and just write some garbage. >so that programs won't trample all over each other. To my knowledge, IBM >PC's do not have this. IIgs's do. The reason people are making MMUs is >NOT because software versions do not work, it's simply because it's less for >the software to do. And we ALL know that, in general, hardware does things >quite a bit faster than software. No, people make MMUs for the reason above - to keep processes from reading and writing another processes space accidentally. And yes, BIOS does have a memory allocation package. It's No Big Deal, you know. > >By the way, if you don't want your IIgs, please send it to me. I'd be >more than happy to accept it. Some of us who don't have all that much money >are grateful for such gifts. Oh, give me a break. > >- Andrew. aabenson@balance.cs.mtu.edu Bitnet: AABENSON@MTUS5.BITNET Patrick Wetmore P.S. multitasking in an unprotected environment is not good, if you do any kind of real work at all. -- +------------------+ Could you fancy me as a pirate bold |Patrick J. Wetmore| Or a longship Viking warrior with the old gods on his side |floyd@pawl.rpi.edu| Well, I'm an inshore man and I'm nobody's hero +------------------+ But I'll make you tight for a windy night and a dark ride