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Date:      Fri, 8 Dec 2000 20:55:44 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        msmith@FreeBSD.ORG (Mike Smith)
Cc:        smp@FreeBSD.ORG
Subject:   Re: Netgraph and SMP
Message-ID:  <200012082055.NAA22567@usr01.primenet.com>
In-Reply-To: <200012080542.eB85gVN00523@mass.osd.bsdi.com> from "Mike Smith" at Dec 07, 2000 09:42:31 PM

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> > Er, what are you smoking Terry?  You never 'update' the cache on another 
> > processor; the other processor snoops your cache/memory activity and 
> > invalidates its own cache based on your broadcasts.
> 
> I should have added "if you're lucky" to this.  Some platforms don't even 
> go that far.

The BeBox is an example of a box without an L2 cachem and using
the L2 cache control lines in order to implement MEI coherency
for a maximum of two CPUs.

You can actually get zero cycle bus arbitration to work with
multiple MIPS processors (Phil Neiswanger initiated some work
on this; I helped with the arbitration algorithm), also giving
MEI coherency.

I understand the limitations; please see my other posting.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.


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