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Path: utzoo!mnetor!seismo!lll-crg!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: net.micro.mac
Subject: Re: Application Heap Jockeying
Message-ID: <1053@hoptoad.uucp>
Date: Wed, 3-Sep-86 05:27:33 EDT
Article-I.D.: hoptoad.1053
Posted: Wed Sep  3 05:27:33 1986
Date-Received: Wed, 3-Sep-86 18:48:29 EDT
References: <250@iscuva.UUCP>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Distribution: net
Organization: Centram Systems, Berkeley
Lines: 33
Summary: Don't even try to do this

In article <250@iscuva.UUCP> jimc@iscuva.UUCP (Jim Cathey) writes:
>Help!  I am trying to write an application program for my 512E Mac to
>permanently move the application heap from where it is normally to an
>extra 1MB of non-contiguous ram that I usually use as a non-volatile
>RAMdisk.  I would prefer to leave the system heap where it is (perhaps
>bumping the size to encompass the range normally used by the
>application heap).  Right now, all I get is a system bomb (no specified
>number as it doesn't get that far) when I try.  Is there any way to do
>this?

You can do it, but you will have to patch in your own versions of Launch and
ExitToShell.  This is a good deal of work, but it can be done.  Do not muck
about with the layout of a process in memory!  I assume you were going to do
this from your note that you are disabling the stack sniffer.  Many
applications, notably a little thing known as the Finder, depend on the
stack being right above ApplLimit.

You are almost guaranteed to run into a lot of uanticpated problems and
tricky debugging when monkeying with these parts of the operating system, so
don't even try this if you are thinking about a weekend project.  It will be
hard, and you will have to know a lot about the Mac OS.  There is also some
very delicate assembly-language coding involved....

I don't know about your hardware configuration, but if it was purchased from
somewhere else or built as a kit, and it is billed as only a RAM disk, I'd
be willing to wager that you can't grow MemTop the way you are trying to do,
or otherwise use it as other than a RAMdisk.
-- 
Tim Maroney, Electronic Village Idiot
{ihnp4,sun,well,ptsfa,lll-crg,frog}!hoptoad!tim (uucp)
hoptoad!tim@lll-crg (arpa)

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