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From: daveh@cbmvax.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: Commodore 68020
Message-ID: <2844@cbmvax.UUCP>
Date: Mon, 23-Nov-87 14:28:29 EST
Article-I.D.: cbmvax.2844
Posted: Mon Nov 23 14:28:29 1987
Date-Received: Thu, 26-Nov-87 04:29:28 EST
References: <21872@ucbvax.BERKELEY.EDU>
Distribution: na
Organization: Commodore Technology, West Chester, PA
Lines: 38

in article <21872@ucbvax.BERKELEY.EDU>, shs@ji.Berkeley.EDU (Steve Schoettler) says:
> 
> In article <177@vertigo.UUCP> rusty@vertigo.UUCP (91341-M.W.HADDOCK) writes:
>>  The memory starts at address 0x7f000000,
>>
>>					-Rusty-

> It turns out that the best Prolog implementations (to date) are on tagged
> architectures.  ...

> Thus, if a 68020 board has memory above 0x0fffffff, prolog won't be able
> to access it.

It's a little more involved that that, Boso!  Anything that uses upper bits
as tagged won't work on any 68020 system that does fully decoded addressing.
So if my memory board is at, say, 0x01000000, it's not going to be at 
0x11000000 or 0x21000000, etc. if I'm fully decoding the 68020 addresses.

> To others who know:
>   Can the CSA board be jumpered to use another address space?
>   Do other Amiga 68020 cards (like Finally, CBM, ASDG) put memory way
>   up there?

The Amiga 68020 card doesn't put memory "up there", but like I explained,
it's not the location that matters.  The Amiga board DOES have an MMU.
This would allow you to map "up there" memory "down here", and (what's
more important for tagged systems), MAY let you program memory wrapping, so
your tags don't affect anything (I haven't actually tried this, but I 
suspect it would work).  

What you really want is the TI LISP chip on a coprocessor card.

> -Steve Schoettler

-- 
Dave Haynie     Commodore-Amiga    Usenet: {ihnp4|caip|rutgers}!cbmvax!daveh
   "The B2000 Guy"              PLINK : D-DAVE H             BIX   : hazy
		"I can't relax, 'cause I'm a Boinger!"