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From: mystone@mondo.engin.umich.edu (Dean Yu)
Newsgroups: comp.sys.mac.programmer,comp.sys.mac.misc
Subject: Re: ROM in RAM
Message-ID: <1990Oct31.162230.3292@engin.umich.edu>
Date: 31 Oct 90 16:22:30 GMT
References: <1990Oct31.032509.265@bushido.uucp>
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In article <1990Oct31.032509.265@bushido.uucp> kr1@bushido (kahlil rowter) writes:
>I have been using MacMeter for a while now. I've noticed that my SE/30 
>typically spends 50-70% of the time on ROM accesses (no surprise here
>right?). So I thought of the ability of 386 (DOS) machines to load its
>ROM in RAM thereby cutting down access time and improving overall thruput.
>Now comes the hard question: Has there been attempts to load the Mac ROM
>onto RAM? If not, why?
>

  On the Macintosh, ROM is at least as fast as RAM, probably faster, so that's
one reason not to bother.  Then there is the size of the ROM.  If you copied
the ROM into RAM, you'd suck up anywhere between 128K to 512K of your
memory.  (Not that it really matters these days, but I like lots of free RAM.)
The last reason, and probably the most important is that this would break
every single come-from patch, since they check the return address on the
stack, and of course, moving ROM to RAM would cause these return addresses to
change.

_______________________________________________________________________________
Dean Yu                            | E-mail:    mystone@mondo.engin.umich.edu
Patches 'R' Us                     | Real-mail: Dean Yu
A Division of Cyberite Systems     |            909 Church St Apt C
                                   |            Ann Arbor, MI 48104
I'm not the voice of Reason, much  | Phone:     313 662-4073
    less the voice of Cyberite.    |            313 662-4163
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