Path: utzoo!attcan!uunet!peregrine!elroy!ames!lll-tis!oodis01!uplherc!esunix!jsnow
From: jsnow@esunix.UUCP (John Snow)
Newsgroups: comp.sys.apple
Subject: Re: 65816 v. 680x0
Message-ID: <1085@esunix.UUCP>
Date: 16 Nov 88 03:16:53 GMT
References: <8811132232.aa14565@SMOKE.BRL.MIL>
Organization: Evans & Sutherland, Salt Lake City, Utah
Lines: 21

From article <8811132232.aa14565@SMOKE.BRL.MIL>, by AWCTTYPA@UIAMVS.BITNET ("David A. Lyons"):
> 
> The 68000 series *before* the 68030 provides a 24-bit address bus
> just like the 65816's, allowing 16 Megs of addressible physical
> memory.  The 68030 supports a memory-management chip that provides
> a 4 Gigabyte (4096 Megabyte) virtual memory space.
> 
No, the 68020 and the 68030 both support a full 32-bits of physical
address space without the need for the memory-management hardware.  The
680x0 family has always had 32-bit address registers and all instructions
respected the 32-bit address space, but the 68000 and 68010 only had
24-bit address buses.  With the advent of the 68020, and later the 68030, 
the address bus was expanded to a full 32-bits.  The memory management
hardware is only necessary if you wish to implement virtual memory -- it
does not expand the size of the address space.
 
-- 
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John F. Snow                         UUCP:{ucbvax,decvax}!decwrl!esunix!jsnow 
Evans & Sutherland Computer Corp.    Compuserve: 71550,1152    BIX: johnfsnow
Salt Lake City, Utah                 "Apple ][ forever!"