Path: utzoo!mnetor!uunet!husc6!think!ames!pacbell!att-ih!ihnp4!chinet!dag
From: dag@chinet.UUCP (Daniel A. Glasser)
Newsgroups: comp.sys.m68k
Subject: Re: Apollo/Sun 68000,68010,68020
Message-ID: <4368@chinet.UUCP>
Date: 31 Mar 88 02:18:00 GMT
References: <3b219db7.d858@apollo.uucp> <903@cayman.COM> <1525@puff.cs.wisc.edu>
Reply-To: dag@chinet.UUCP (Daniel A. Glasser)
Organization: Chinet - Public Access Unix
Lines: 30

In article <1525@puff.cs.wisc.edu> richardk@puff.WISC.EDU (Richard Kottke) writes:
>>No doubt 600 others will also respond to this. The issue here is not
>>preemptive multitasking ("What bubba meant to say was...") The issue
>>here is recovering from a bus error. The demand paging support (read
>
>  Recovering from a bus error is a problem only if the system uses a virtual
>memory scheme (which it would if it was running UN*X.)  If the system was
>running, say, OS-9/68k, then virtual memory is not required and the bus error
>is a real bus error, not a flag indicating that a new page needs to be brought
>in.

I believe that the dual-68000 machines did support virual memory...
One 68k was a little ahead of the other, and when the first would have
a buss error, the second would be stopped until the first had corrected
the situation that caused the buss error.  The second would then be
interrupted and its state loaded into the first, and both would then
continue as if nothing had happened.  That was the point of the dual 68k's.

Somehow I get the impression from reading the article to which this is
a follow-up that people have forgotten that Unix runs on machines without
virtual memory, and that Unix was originally designed for machines without
virtual memory.  It was not until a few years ago that Unix on a Vax
actually supported demand paging for process growth and swapping.

I run UNIX on a machine without paged memory.

-- 
		Daniel A. Glasser	dag@chinet.UUCP
    One of those things that goes "BUMP!!! (ouch!)" in the night.
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