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From: jack@Taffy.rice.edu (Jack W. Howarth)
Newsgroups: comp.sys.mac.hardware
Subject: Re: The future of the past mac
Keywords: obsolescence
Message-ID: <1990Nov17.230151.9843@rice.edu>
Date: 17 Nov 90 23:01:51 GMT
References: <1990Nov11.114837.26676@rodan.acs.syr.edu> <1990Nov11.175402.4291@rice.edu> <1990Nov12.122654.9692@rodan.acs.syr.edu>
Sender: news@rice.edu (News)
Organization: Rice University
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>I'm using 16MB (4M physical). I understand that NuBus has something to do with
>the 14MB limit on the IIs.
>
>-- 
>*******************************************************************************
>* Bill Taroli (WWTAROLI@RODAN.acs.syr.edu)    | "You can and must understand  *
>* Syracuse University, Syracuse NY            | computers NOW!" -- Ted Nelson *
>*******************************************************************************
 
Bill,
   The VM on the II series of Mac's (that includes the SE/30 which has
essentially IIx ROMs) is implemented giving the VM access to memory mapped
to each NuBus slot. The Nubus slots get 1 meg each. As the Mac and video
card each are a slot, only 6 extra meg can be assigned beside the 8 meg
available through the motherboard's simm slots. It is my understanding that
32 bit clean ROMs (aka IIci, IIfx or IIsi) are required to get more than 
8 meg real or 14 meg virtual memory. When if ever Apple will do a ROM upgrade
for the II, IIx, IIcx and SE/30 is another question. My guess is they won't
and we'll be locked at 14 meg VM until Apple implements premptive multitasking
and protected memory in System 8.0 which would require yet another ROM
upgrade. On the otherhand by then Apple may assume we'll dump our II's like
we did the 128 and 512 K Macs and buy newer models.
                              Cheers...
                                   Jack
p.s. Apple sells hardware, the system software is just part of the packing material...