Path: utzoo!mnetor!uunet!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: Still More 68020 Questions
Message-ID: <3136@cbmvax.UUCP>
Date: 12 Jan 88 17:16:04 GMT
References: <8822@ccicpg.UUCP>
Organization: Commodore Technology, West Chester, PA
Lines: 28

in article <8822@ccicpg.UUCP>, harald@ccicpg.UUCP ( Harald Milne) says:

> 	Well this has not been discussed at great length.

> 	I read this article, and was suprised to learn that the 68020
> would run slower than the 68000.

> 	I got an answer from fellow engineers working with 68020 controllers.
> 
> 	The 68020 works well with a 32 bit bus. The Amiga is 16. When the
> 68020 requests a 32 bit quanity like an address, it has to generate 2
> address requests to retrieve this data. More time spent in bus transfers.

What you're missing here is that, in most cases, the 68000 would also have
to run two memory cycles.  The 68000 works with 32 bit addresses just like
the 68020, even if only 24 bits of those addresses are considered significant.
With the cache enabled, we've found a 68020 board, depending on design, can
run somewhat faster than a 68000 out of slow 16 bit memory.  Give it fast
32 bit memory and you're talking about a 3x-4x speed increase.

> -- 
> Work: Computer Consoles Inc. (CCI), Advanced Development Group (ADG)
>       Irvine, CA (RISCy business! Home of the CCI POWER 6/32)
> UUCP: uunet!ccicpg!harald
-- 
Dave Haynie  "The B2000 Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {ihnp4|uunet|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
		"I can't relax, 'cause I'm a Boinger!"