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From: bdugan@teri.bio.uci.edu (Bill Dugan)
Newsgroups: comp.sys.mac.hardware
Subject: Re: How much memory I can have in Mac classic ?
Message-ID: <2791B723.7910@orion.oac.uci.edu>
Date: 14 Jan 91 13:50:27 GMT
References: <1991Jan14.024726.22891@Veritas.COM> <6730@wolfen.cc.uow.oz>
Reply-To: Bill Dugan <bdugan@teri.bio.uci.edu>
Organization: University of California, Irvine
Lines: 18
Nntp-Posting-Host: teri.bio.uci.edu

In article <6730@wolfen.cc.uow.oz> sam@wolfen.cc.uow.oz (Sam Tan) writes:
>This is the memory layout in a Classic:
>
>There is 1 MB of RAM soldered on the mother board.
>
>Apple sell a memory expansion card that has 1 MB soldered on there, but
>with 2 empty SIMM slots. You can put it anything you want in the SIMM slots
>but you must do it in pairs. You can only go up to 8 MB on a Classic, although
>the ROM is 32-bit clean. This is due to the lack of a true PMMU system.

This is not true!  The Mac Classic can only have 4 megs of RAM, same as
a Plus or SE.  And the PMMU's presence or absence doesn't have anything
to do with the arbitrary eight-meg limit on the Mac II line; the problem
came from the memory layout Apple 'decided to have' when they wrote the
ROMs in the first place.  System 7 will let you have up to 128 Mb of
directly addressed RAM, and this is not dependent on a PMMU.

bill