Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!swrinde!ucsd!ucsdhub!celit!rory
From: rory@fps.com (Thomas (Rory) Bolt)
Newsgroups: comp.sys.mac.hardware
Subject: Re: IIci and Video (was Re: IIci + 8Mb != more speed)
Summary: Oh those MMU's!
Keywords: MMU, IIci
Message-ID: <6906@celit.fps.com>
Date: 16 Feb 90 01:10:09 GMT
References: <22499@mimsy.umd.edu> <25d88b45.2cea@polyslo.CalPoly.EDU> <22513@mimsy.umd.edu> <1990Feb14.170610.26797@agate.berkeley.edu> <22563@mimsy.umd.edu>
Sender: daemon@fps.com
Reply-To: rory@fps.com (Thomas (Rory) Bolt)
Distribution: usa
Organization: Bolt Technologies
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One interesting thing to note is that the physical memory map of the IIci is NOT
contiguous. If you get into MacsBug 6.1 and type "TM" to display the MMU
registers and take the time to decode the page table entries, you will find that
the MMU will map virtual addresses in the range 0 to 4 Mbytes to the bank B RAM
if you have 8 Mbytes installed. This would tend to suggest that you would actually
want to load your programs into LOW memory for maximum execution efficiency. As
a side issue, since the upper half of the 8 Mbyte space is actually mapped to
bank A RAM, references to the stack & possibly the heap MAY be the culprits! I
have not gathered enough evidence to give a definitive answer to the question
of how best to load programs in the IIci.

					Rory Bolt