Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!samsung!usc!zaphod.mps.ohio-state.edu!swrinde!ucsd!ucbvax!GAR.UNION.EDU!91_bickingd From: 91_bickingd@GAR.UNION.EDU ("Bicking, David") Newsgroups: comp.sys.amiga Subject: REAL, TRUE, Honest-to-God Multitasking. Message-ID: <9101110001.AA18145@ucbvax.Berkeley.EDU> Date: 10 Jan 91 22:58:00 GMT Sender: daemon@ucbvax.BERKELEY.EDU Lines: 72 Date sent: 10-JAN-1991 18:43:19 >multitasking system. If the user expects program not to multitask, and >the exceptions are magic programs (TSRs, desktop accessories, >whatever) that can run while a "normal" program runs - then you don't >have a multitasking system. > > Again, my original point was that a much larger segment of the industry > counts non-preemptive multitasking as not quite "true" multitasking. It > wasn't the Amiga folks who made it up, though you are correct in that some > of them do tend to yell too loudly about it simply to make themselves > feel superior to Machine X, often without really understanding the real > differences. This must be quantified.... > >Well, I managed to miss the rest of the industry doing it, so I assume >others have done the same. Amiga users dropping that usage would help >their image. Since I object to the usage, it'd also make me feel >better. You may object to the usage, but too bad. I object to Apple calling Hypercard applications multitasking, but I'm going to have to live with it. >Then again, I'll could decide that "true" multitasking means "no task >can ever be completely blocked out, unless the user specifically >allows it to happen by tagging the blocked task". That makes a lot >more sense to me than just not allowing low priority tasks to starve >higher priority ones. But then the Amiga doesn't have "true" >multitasking. Time to do the quanitfying I mentionned above. I am currently learning about operating systems in college. I now understand the difference between Unix multitasking and amiga multitasking and "other" multitasking. The Amiga uses a "Round-Robin" scheduler. This means the _OS_ gives every TASK/Process equal time, preempting a task after a fixed clock period and moving to the next task. This means, obviously, that shorter/smaller tasks will be finished before long ones, but the longer ones will not starve (be denied the CPU). Under this system, all tasks are preempted by the OS (unless some special option is used to override. Such a command exists on the amiga), and the program doesn't need to do anything special to multitask, but must do something special to hog the CPU. Unix uses a "Multiple Feedback Queue" scheduler. This has much more overhead, as larger tasks are shoved on lower-priority queues to permit the shorter tasks to hog the CPU and get their job over-with faster. With this scheduler, cpu-intensive tasks could conceivably starve. The prof says that this is a "more efficient" scheduler than the round-robin one, but I tend to disagree. Then there is the MAC and the IBM. The OS has no clue about multitasking. Programs must be written to work at the same time as others ( TSRs and Multifinder apps). This is, strictly speaking, multitasking. H owever, Engineers and Computer Science people do not generally consider it multitasking because it is not PREEMPTIVE. The MAC and IBM (under dos/windows) do not multitask. The stuff written that runs while other stuff runs are " kludges" in the sense that they act outside the OS in that respect. I can see already that my dialogue is getting abstract and muddy, so I will stop. I've begun to speak from opinion. OS/2, I believe, does multitask preemptively. Don't hold me to that statement though, I know little about it :) -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=- Dave Bicking Single Tasking????? Just say NO!!!! Union College Box 152 91_bickingd@union.bitnet // Schenectady, NY 12308 91_bickingd@gar.union.edu \X/ Amiga -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-