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Date:      Thu, 5 Oct 2000 23:28:05 +0200
From:      Wilko Bulte <wkb@freebie.demon.nl>
To:        Doug Rabson <dfr@nlsystems.com>
Cc:        Matthew Jacob <mjacob@feral.com>, FreeBSD-alpha mailing list <freebsd-alpha@freebsd.org>
Subject:   Re: max memory on Alpha?
Message-ID:  <20001005232805.B7134@freebie.demon.nl>
In-Reply-To: <Pine.BSF.4.21.0010042345000.94692-100000@salmon.nlsystems.com>; from dfr@nlsystems.com on Wed, Oct 04, 2000 at 11:46:29PM %2B0100
References:  <20001003212847.A1868@freebie.demon.nl> <Pine.BSF.4.21.0010042345000.94692-100000@salmon.nlsystems.com>

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On Wed, Oct 04, 2000 at 11:46:29PM +0100, Doug Rabson wrote:
> On Tue, 3 Oct 2000, Wilko Bulte wrote:
> 
> > On Tue, Oct 03, 2000 at 11:57:55AM -0700, Matthew Jacob wrote:
> > > On Tue, 3 Oct 2000, Wilko Bulte wrote:
> > > 
> > > > What is the currently max supported memory size on Alpha? 2Gb maybe?
> > > > Or will 4Gb also be OK?
> > > > 
> > > > Reason for asking is that I want to try a AS8400 who is equipped
> > > > with 3x 4Gb memory module.
> > > 
> > > I've run 8400s up to 2GB. Any more than that and you'll find that S/G
> > > DMA hasn't been finished ;-).
> > 
> > Well, on 12Gb it panics with pmap_foo <don't remember what foo was
> > off the top of my head> on 4.1-R ;-) Might this mean it cannot create the
> > necessary page table admin on > 2Gb?
> > 
> > Do you know *if* there is a hard limit at 2Gb?
> 
> I don't think there is a *hard* limit for the basic VM system but I
> imagine it might have problems finding a large enough contiguous region to
> map the vm_page_t structures. The main limitation is in the i/o system as
> previously noted.

From looking at the code it would be instructive to compile a kernel
with DEBUG_CLUSTER and see what is says (hopefully before panicing ;-)

I need a sensible -current built first (my -current disk that I carry
around from machine to machine is a bit whacko). Hmm, or maybe -stable
is easier.. Will see what I can do.

W/
-- 
Wilko Bulte  	 
wilko@freebsd.org 			Arnhem, the Netherlands


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