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From: tmb@talcott.UUCP (Thomas M. Breuel)
Newsgroups: net.arch,net.micro.16k,net.micro.68k
Subject: Re: 24 bit vs. 32 bit address space
Message-ID: <344@talcott.UUCP>
Date: Sat, 9-Mar-85 15:24:14 EST
Article-I.D.: talcott.344
Posted: Sat Mar  9 15:24:14 1985
Date-Received: Tue, 12-Mar-85 20:06:12 EST
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Organization: Harvard University
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> I hear Apple is using the top byte on the Macintosh addresses.  Seems like
> this is going to make it difficult for them to port their software to the
> 68020.  Seems to me that using the upper byte of a 68000 address is just

I doubt that using the upper 8 bits will give problems in porting
MacIntosh software:

-- use of the upper 8bits is in most cases hidden in the ROM (i.e.
   most applications don't even know about it).
-- the 68000 already uses all 32bits in address calculations. The only
   way you would have to modify the code using the upper 8bits is
   if you have more than 16M of memory or a memory management unit
   which objects to bits 24-31 being set.

						Thomas.