Path: utzoo!mnetor!uunet!husc6!think!ames!claris!apple!goldman
From: goldman@Apple.COM (Phil Goldman)
Newsgroups: comp.sys.mac
Subject: Preemption vs. VM
Message-ID: <7705@apple.Apple.Com>
Date: 16 Mar 88 08:30:44 GMT
Reply-To: goldman@apple.UUCP (Phil Goldman)
Organization: Apple Computer Inc, Cupertino, CA
Lines: 24


In article <7681@agate.BERKELEY.EDU> mwm@eris.UUCP (Mike (My watch has windows) Meyer) writes:
>[Followups have been pointed to comp.sys.68k.]
>
>In article <7670@apple.Apple.Com> goldman@apple.UUCP (Phil Goldman) writes:
><I think one point you are both missing out on is that preemptive multitasking
><requires hardware support not available on a 68000.
>
>Right. So how did Sun, Apollo, Amiga, Sage, Stride and a multitude of
>others manage to market 68000 systems that did preemptive
>multitasking?
>...
>Here is where the 68000 has problems: there's not enough information
>around to restart a process that page faults in the middle of some
>instructions. The 68010 & later processors fixed this. But people
>found ways around that problem with thoe 68000.

I stand (very) corrected.  I was confusing doing VM on 68000 w/ preemption.
In VM it is impossible to restart the instruction if it causes a page fault,
but as far as a generic interrupts (i.e. not addr err and bus err) go this is
definitely possible on the 68000.  Please excuse my last (late night) posting.

-Phil Goldman
Apple Computer