Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!mit-eddie!uw-beaver!fluke!kurt
From: kurt@tc.fluke.COM (Kurt Guntheroth)
Newsgroups: comp.sys.amiga
Subject: Re: MY Wishlist for A3000
Message-ID: <2320@sputnik.COM>
Date: Mon, 23-Nov-87 16:18:02 EST
Article-I.D.: sputnik.2320
Posted: Mon Nov 23 16:18:02 1987
Date-Received: Thu, 26-Nov-87 07:03:59 EST
References: <74@mithras> <33314@sun.uucp> <2224@sputnik.COM> <5887@jade.BERKELEY.EDU>
Sender: news@tc.fluke.COM
Organization: John Fluke Mfg. Co., Inc., Everett, WA
Lines: 31
Summary: I meant what I said and I said what I meant...

<<In article <2224@sputnik.COM> kurt@tc.fluke.COM (Kurt Guntheroth) writes:
<<(1) Protected virtual memory.  I will not buy ANY computer without this
<<    feature from now on.  This is the critical feature that keeps a
<<    multitasking machine from crashing when a program goes crazy.  With VM,
<<    I can reliably keep the system up for days.

<mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer) writes:
<Carefull. That's two features, one of them ambiguous. Virtual memory
<means either "demand paging" (i.e. - the memory looks like it's there,
<but may not be) or "mapped memory" (i.e. - the memory isn't where you

True, two features, but I did say PROTECTED, VIRTUAL memory.  I require
protected memory so one task doesn't crash another (or the kernel).  I
require virtual memory so I am not limited to the size of my physical memory
or in the number or configuration of programs I may run, either of which may
be surprising over a period of days.

I am aware that all I need do is buy 888 Mbytes of memory and I can run
concurrently all the software ever written for the Amiga.  But I can't
afford 888 Mbytes.  If I have virtual memory, I can 'run' any program,
paying only a speed penalty if there is not enough real memory.

As for people saying virtual memory operating systems are too inefficient, I
suggest you read comp.sys.atari or Pournelle's article in Byte and see what
they are saying about multitasking.  A VM system is as efficient as a non-VM
system under the same circumstances.  Give me 2 Mbytes of real memory, let me
load 1 Mbyte of code into it, and run it concurrently or non-concurrently.
Then show me where the VM is slowing me down.  Oh sure, if the OS or MMU is
brain-dead it may take too long to context switch, but that doesn't indict the
method.  A program may start up FASTER under a demand paged VM than a non-VM
system?  With VM, you can start as soon as the first lines of code are loaded.