Path: utzoo!utgpu!watserv1!watmath!att!att!linac!uwm.edu!zaphod.mps.ohio-state.edu!samsung!dali.cs.montana.edu!milton!phaedrus
From: phaedrus@milton.u.washington.edu (Mark Phaedrus)
Newsgroups: comp.sys.mac.system
Subject: Re: ROM Disk (was Re: Resedit)
Message-ID: <11818@milton.u.washington.edu>
Date: 28 Nov 90 06:47:12 GMT
References: <1990Nov22.050513.6184@CAM.ORG> <128127@tiger.oxy.edu> <1990Nov25.211747.1122@midway.uchicago.edu>
Organization: University of Washington, Seattle
Lines: 24

In article <1990Nov25.211747.1122@midway.uchicago.edu> francis@magrathea.uchicago.edu (Francis Stracke) writes:
>Does anybody know *why* Apple decided to copy the ROM disk into
>RAM? Surely most of it doesn't need to be written!

     Mac programs are guaranteed a writeable boot disk and a writeable System
Folder; it's where they're allowed (nay, demanded) to store temporary files
and such.  A non-writeable boot disk would break just about everything out
there, including lots of Apple's own stuff (even some of the Control Panel
devices don't work on a write-protected boot disk).

>(And it could be set up to use RAM only when it's been changed.)

     This could probably be done, but could lead to all kinds of problems.
The Apple IIgs has almost exactly that same feature; a RAM disk that expands
as you add files.  (You're proposing a ROM disk that gradually copies itself
to such a RAM disk as it changes, if I understand you correctly.)  Any Apple
IIgs owner knows never to use it that way.  The reason: what if the system
can't find the memory to expand the disk when it needs it?  And if a write
to the boot disk fails, it tends to produce rather impressive crashes.

-- 
Internet: phaedrus@u.washington.edu        (University of Washington, Seattle)
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