Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!samsung!viewlog.viewlogic.com!peter
From: peter@suntan.viewlogic.com (Peter Colby)
Newsgroups: comp.sys.mac.system
Subject: Re: SE/30 VM trouble in System 7
Message-ID: <1991May29.142650.27102@viewlogic.com>
Date: 29 May 91 14:26:50 GMT
References: <2842d41f.4648@petunia.CalPoly.EDU>
Sender: news@viewlogic.com
Distribution: usa
Organization: Viewlogic Systems, Inc., Marlboro, MA
Lines: 35
Originator: peter@hari
Nntp-Posting-Host: hari


In article <2842d41f.4648@petunia.CalPoly.EDU>, mjohnson@cosmos.acs.calpoly.edu (Mark S. Johnson) writes:
|> 
|> 
|> I'm running the release System 7 with no inits on a 5 Meg SE/30 with
|> an Apple internal 40 Meg HD. When I turn on VM with the default
|> settings and then reboot, "About This Macintosh" says:
|> 
|> Built-in Memory:   5120 K
|> Total Memory:    10,240 K
|> 10,240 K used as RAM on HD
|> 
|> VM has claimed an extra 5 Megs, and the available disk space reported
|> in Finder windows also shows that an EXTRA 5 Megs have disappeared.
|> 
|> Anyone else see this behavior? Is this a bug, or have I made a blunder?
|> Thanks, Mark

	Not a bug.
	Think about what virtual memory is... Essentially, your physical
memory (Built-in Memory here) acts as a high speed cache for the virtual
memory (Total Memory, which in this case resides on the hard disk). What
this means is that ALL your memory resides in the virtual memory with
copies of the most recently used addresses also living in the "cache".
	What this means is that the amount of "physical memory" has no
relation to the total amount of virtual memory. Just as the file cache
(system 4.1 and higher) didn't increase the total space on your disk,
and the PMMU cache in the 68030 doesn't increase the total physical
memory in your machine, the amount of physical memory you have doesn't
increase the total virtual memory you have allocated.
	pc
-- 
      (O)(O)(O)(O)(O)(O)(O)(O)(O)     (O)(O)(O)(O)(O)(O)(O)(O)(O)
      (O) !the doctor is out! (O)     (0) peter@viewlogic.com (0)
      (O)(O)(O)(O)(O)(O)(O)(O)(O)     (O)(O)(O)(O)(O)(O)(O)(O)(O)