Path: utzoo!mnetor!uunet!husc6!bbn!rochester!ritcv!cci632!ccicpg!leo!harald
From: harald@leo.UUCP ( Harald Milne)
Newsgroups: comp.sys.amiga
Subject: Re: 68030 Questions
Message-ID: <1857@leo.UUCP>
Date: 5 Feb 88 12:02:38 GMT
References: <10170@ccicpg.UUCP> <3246@cbmvax.UUCP>
Organization: CCI CPD (Advanced Development), Irvine CA
Lines: 44

In article <3246@cbmvax.UUCP>, daveh@cbmvax.UUCP (Dave Haynie) writes:
> in article <10170@ccicpg.UUCP>, harald@ccicpg.UUCP ( Harald Milne) says:
> > 	The only problem I can imagine at this point, is DMA to FAST ram. 
> > Would anybody be silly enough to do this? This will kill the 680x0.
> 
> This happens all the time with things like hard disk drives.  It sure does
> hurt the 68000's speed, but consider the alternative. 

	I'm painfully aware of the alternative. My question was a bit rhetorical.
I have an A1000 at home with HD and 1.75meg, and an A2000 at work with
Ethernet and 3meg. You are right, you have to DMA to get reasonable 
performance. My reference to 680x0, was in reference to the 68030, 68020,
68000. And the best solution overall. More specifically, the 68030.

	I think we have hit the hard spot.

	Solutions? Hmm....

	Somehow, for the 68030 at least, you have to invalidate these entries
in the cache, or prevent them from ever appearing.

	To invalidate, is a software solution.

	To prevent it from appearing, could possibly be done by hardware. Or even
by a combination of hardware/software via the MMU.

	The real question is, which yeilds the most performance, while maintaining
compatability.

	Hmmm.... I have to think about this a bit. This gets even tougher when you
consider all the possible configurations, memory timings, etc. Ack!

	Looks like your prophecy in AC comes true after all, "And on the '020 vs.
'030 question, we may have a surprise or two you aren't considering."

	This sure gives me enough to chew on.

> 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!"
-- 
Work: Computer Consoles Inc. (CCI), Advanced Development Group (ADG)
      Irvine, CA (RISCy business! Home of Regulus and hamiga)
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