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From: Jim.Spencer@p510.f22.n282.z1.fidonet.org (Jim Spencer)
Newsgroups: comp.sys.mac.misc
Subject: Re: The Fate of the Macintosh
Message-ID: <670469109.3@mmug.fidonet.org>
Date: 31 Mar 91 15:42:56 GMT
Article-I.D.: mmug.670469109.3
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Lawrence Reed Miller writes in a message to All

LRM> Much of the Mac toolbox is in ROM, but there is no reason that 
LRM> the toolbox traps can't be stored in RAM. In fact, that's how 
LRM> Apple updates the toolbox--traps that are not in ROM, or which 
LRM> have been changed are loaded into RAM out of the System File. 
LRM> Of course, to do this legally you would have to come up with 
LRM> an independant verson of the Mac Toolbox and System Software. 
LRM> This would be difficult, but certainly not impossible.

Actually the trap dispatcher is in RAM even for those routines which are not patched.  A copy gets copies from ROM and then patches modify it as necessary to cause patched routines to jump to the new code.