Path: utzoo!utgpu!watmath!att!dptg!rutgers!tut.cis.ohio-state.edu!ucbvax!hplabs!hpda!hpdslab!hp-ptp!davew From: davew@hp-ptp.HP.COM (Dave_Waller) Newsgroups: comp.sys.mac Subject: Re: Hey Apple Mac engineers, I want an answerO!! Message-ID: <1570011@hp-ptp.HP.COM> Date: 14 Aug 89 18:57:49 GMT References: <577@studsys.mu.edu> Organization: HP Pacific Technology Park - Sunnyvale, Ca. Lines: 32 ts@cup.portal.com (Tim W Smith) writes: > Ok, I give up. Where did you get the idea that multitasking > requires virtual memory? > > Tim Smith > ---------- Well, Tim, it doesn't REALLY, but VM sure makes it a hell of alot easier to implement. With VM, as far as the processor is concerned, EVERY process' Working Set is in memory, allocated to a different piece of a very large virtual addressing space. When it comes time to process switch, the dispatcher need not decide whether or not a process' WS is actually in physical memory, it simply switches to the process and allows the WS to page fault in with the VM handler if it isn't in memory. Ask anyone who's tried to implement a clean multitasking system without VM, and they'll tell you being strapped to a truck tire on a cross country trip would be more fun. Dave Waller Hewlett-Packard Co. Workstation Group Pacific Technology Park 1266 Kifer Rd. Sunnyvale, CA (408) 746-5324 [ucbvax!]hplabs!hpdstma!dave | dave@hpdstma.ptp.hp.com +-------------------------------------+---------------------------------------+ | Standard disclaimer: | "I refuse to put anything in quotes | | The opinions expressed above are | in this space" | | solely my own, and in no way reflect| | | those of my employer. | | +-------------------------------------+---------------------------------------+