Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!uunet!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.emulations
Subject: Re: A3000/AMax Problems
Message-ID: <18024@cbmvax.commodore.com>
Date: 24 Jan 91 21:07:42 GMT
References: <1114@macuni.mqcc.mq.oz>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 31

In article <1114@macuni.mqcc.mq.oz> ifarqhar@sunb.mqcc.mq.oz.au (Ian Farquhar) writes:

>My friend has a 25MHz A3000 equipped with 16M of RAM.  With this setup,
>AMax installed with 128K ROMS refuses to run.  As a test, the memory was 
>reduced to 9M, and with this configuration AMax ran successfully.
>Nothing else was changed.

>Does anyone have any ideas why this should be so?  

I suspect there's just a little bit of magic here at work.  The current Mac
operating system can only handle 24 bit addressing, basically what you get
with a 68000.  Mac IIs running the Mac OS use the MMU to make everything 
wrap to 24 bits, and I imagine the AMAX II does something similar on the
A3000.  Internal A3000 Fast memory is mapped from $07000000-$07ffffff on that
16MB machine, well out of the 24 bit space used by the 68000 hardware.  With
some MMU tables, you could translate some of this Fast memory into 24 bit
space, but certainly not all of it, since there are I/O regions that must
be taken out of the total 16MB space 24 bit addressing gives you.

Presumably if Apple releases their System 7.0, which reportedly fixes this
problem in the Mac OS (though not necessarily all Mac applications), AND
System 7.0 learns to deal with non-contiguous memory pools (like AmigaOS does),
AND AMAX gets upgraded to do whatever is necessary to live under System 7.0,
than you may get all 16MB free under AMAX.

>Ian Farquhar                      Phone : 61 2 805-9400

-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
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	"What works for me might work for you"	-Jimmy Buffett