Newsgroups: comp.sys.mac.hardware
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!caen!ox.com!math.fu-berlin.de!fauern!NewsServ!breidenb
From: breidenb@Informatik.TU-Muenchen.DE (Oliver Breidenbach)
Subject: Re: System 7.0 and RAM
Message-ID: <1991Apr22.101220.3494@Informatik.TU-Muenchen.DE>
Sender: news@Informatik.TU-Muenchen.DE
Organization: Technische Universitaet Muenchen, Germany
References: <1991Apr12.201532.18426@visix.com> <97@eclectic.COM> <1991Apr22.042204.1291@lynx.CS.ORST.EDU>
Distribution: usa
Date: Mon, 22 Apr 1991 10:12:20 GMT
Lines: 16

In article <1991Apr22.042204.1291@lynx.CS.ORST.EDU> hasses@prism.cs.orst.edu (Stephen Haase) writes:
>One VERY annoying thing I noticed with system 7's virtual memory was that x
>amount of HD space does not equal x amount of extra RAM. I got 7.0fc2 going and
>then tried to add 3 megs of RAM to my 5 physical RAM. It worked all right, but
>it took 8 megs of HD space to give me those extra 3 megs. Needless to say, I
>removed it quickly since I only have 9 megs free anyways. 
that is what "virtual memory" is. The physical space is mapped to a logical one.
That implies that you need to have the whole physical space available somewhere
in order not to loose information. I guess that Apple has choosen to have all
available space on the disk in order to reduce "write-back" operations. They
don't have to write back space that hasn't changed since it was loaded into
ram, like most parts of the applications code.
However, it's just a guess. 

Oliver.

