Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!yale!ox.com!umich!vela!dlcogswe From: dlcogswe@vela.acs.oakland.edu (Dan Cogswell) Newsgroups: comp.sys.amiga Subject: Re: Multitasking vs MultiFinder (was Amy 68030 vs Mac IIcx) Summary: Well... Not really.. Message-ID: <331@vela.acs.oakland.edu> Date: 12 Mar 90 21:44:05 GMT References: <3137@bingvaxu.cc.binghamton.edu> Reply-To: dlcogswe@vela.acs.oakland.edu (Dan Cogswell) Distribution: na Organization: Oakland University, Rochester MI Lines: 39 In article <3137@bingvaxu.cc.binghamton.edu> consp11@bingsunm.cc.binghamton.edu (Brett Kessler) writes: >but I must say, quite simply, that Apple's MultiFinder is a joke, basically >because the hardware itself is still not capable of true multitasking. True, but not for the following reason... >What the MultiFinder does is basically the same thing as the Mac cDEV called >Switcher. It lets you swap out one program and swap in another, but ONLY ONE >IS RUNNING AT ANY GIVEN TIME. The other one is put to "sleep" until it is >switched back in. The Amiga, on the other hand, has the hardware support for >true multitasking. There are custom chips for I/O, sound, graphics, etc., >freeing up the CPU to do more, such as run more than one program at a time. You're talking about different levels of multitasking here. In effect, the Exec and Multifinder do the same thing: they schedule processes for the CPU by putting the current process to sleep, then, based on some algorithm, wake another. ONLY ONE PROCESS IS RUNNING ON THE CPU OF THE AMIGA *OR* THE MAC AT ANY GIVEN INSTANT. PERIOD. The main difference between the two involves the WAY in which the scheduler is allowed to make the context switch. The Amiga Exec is tied into the hardware clock interrupt, which cannot be disabled by software. In other words, a process cannot take hold of the CPU forever (as long as correct programming practices are observed). Multifinder, on the other hand, is not tied to any hardware interrupt, which means a process can grab the CPU and keep it until it decides to let it go. Also, (and I may be wrong on this one), Mac software can busy-wait at times. A big no-no in a multitasking system. The CPU is spinning doing no work. >+------///-+------------------| BRETT KESSLER |------------------+-\\\------+ >| /// | consp11@bingvaxu.cc.binghamton.edu | \\\ | >| \\\/// | consp11@bingvaxa.BITNET | \\\/// | >| \XX/ | (PeopleLink) B.KESSLER | \XX/ | >+----------+-----------------------------------------------------+----------+ -- Dan Cogswell | If *ONE MORE* | Disclaimer: (313)625-3234 | person makes | Oakland University INET: cogswell@vela.acs.oakland.edu | a joke about | doesn't HAVE a cogswell@unix.secs.oakland.edu | "Cogswell Cogs!!"| position on this.