Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!ra!emory!gatech!usenet.ins.cwru.edu!agate!stanford.edu!neon.Stanford.EDU!torrie From: torrie@cs.stanford.edu (Evan Torrie) Newsgroups: comp.sys.amiga.misc Subject: Re: How do we change the scheduler? (Was Re: Multitasking at home...) Message-ID: <1991May13.232625.14013@neon.Stanford.EDU> Date: 13 May 91 23:26:25 GMT References: <7504@sugar.hackercorp.com> <41681@nigel.ee.udel.edu> Sender: torrie@neon.Stanford.EDU (Evan James Torrie) Organization: Computer Science Department, Stanford University, Ca , USA Lines: 37 new@ee.udel.edu (Darren New) writes: >In article jimb@pogo.ai.mit.edu (Jim Blandy) writes: >>A Mac running the Multifinder has non-preemptive multitasking; each >>task voluntarily gives up control. The Amiga does preemptive >>multitasking; a task may be stopped at any time. >It's worse than this. Try starting up multifinder, hypercard, and >(say) tetris. I just did this last night because I wanted to play >tetris but the owner of the machine had the hypercard stack open. >Anyway, the music was all messed up and the blocks fell at different >speeds, making it difficult to play. I then realised that hypercard >must be sucking up CPU time even though it was not active, it was not >running anything, and the mouse was not near the window. ^^^^^^^^^^^^^^^^ Actually, Hypercard is always running something, even when it's sitting in the background. The reason? Hypercard sends "idle" messages to the current chain of control in its object hierarchy when nothing is happening. This allows fields/cards/stacks to perform actions even when nothing is happening. A good example of this is the "Display time continuously" field in the Readymade fields example of HC 2.0. Plunk it in the background, and you'll see that the time continues to update, indicating that the idle message is getting send to the card, which then sends a message to the field, which then updates itself. Since all of this action is via interpreted scripts, HC can quite easily chew up a fair amount of CPU time. >[rest of good expose of cooperative multitasking deleted] -- ------------------------------------------------------------------------------ Evan Torrie. Stanford University, Class of 199? torrie@cs.stanford.edu Where can a nation lie when it hides its organic minds in a cellar dark and grim? They must be ... very dim.