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From: daveh@cbmvax.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: Prolog on 68020
Message-ID: <2845@cbmvax.UUCP>
Date: Mon, 23-Nov-87 14:35:07 EST
Article-I.D.: cbmvax.2845
Posted: Mon Nov 23 14:35:07 1987
Date-Received: Thu, 26-Nov-87 04:29:42 EST
References: <17223@glacier.STANFORD.EDU>
Distribution: na
Organization: Commodore Technology, West Chester, PA
Lines: 23

in article <17223@glacier.STANFORD.EDU>, jbn@glacier.STANFORD.EDU (John B. Nagle) says:
> Summary: Use of high bits in address for other purposes won't work on 68020.
> 
>      Won't work.  The M68020 has an on-chip cache which stores 32-bit
> address values.  Even if the external memory addressing only uses fewer
> bits, the cache always checks all 32.   On a system where the high address
> byte is unused by the memory, the following sequence will produce  
> unwanted effects:

While AmigaOS turns the cache on on system startup, the Prolog interpreter
could turn it off to avoid any problems related to the cache not wrapping.

That's, of course, going to slow things down, but what can you do.

> Like it or not, the M68020 is a 32-bit machine.

And like I said before, what they really want here is a 40-bit machine.

> 				John Nagle
-- 
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!"