From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out.tiscali.be (spoolo2.tiscali.be [62.235.13.211]) by dsl2.external.hp.com (Postfix) with ESMTP id 38F084852 for ; Sat, 21 Feb 2004 11:18:55 -0700 (MST) Message-ID: <4037A133.5020906@tiscali.be> Date: Sat, 21 Feb 2004 18:19:31 +0000 From: Joel Soete MIME-Version: 1.0 To: Matthew Wilcox Subject: Re: [parisc-linux] Linux only see 2Gb of ram of N4k References: <402A4CA500006EA3@ocpmta2.freegates.net> <20040220182140.GC11824@parcelfarce.linux.theplanet.co.uk> In-Reply-To: <20040220182140.GC11824@parcelfarce.linux.theplanet.co.uk> Content-Type: text/plain; charset=us-ascii; format=flowed Cc: parisc-linux@lists.parisc-linux.org List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Matthew Wilcox wrote: > On Fri, Feb 20, 2004 at 07:04:26PM +0100, Joel Soete wrote: > >>Hi all, >> >>My collegue make me notice that the N4k on which I can test Linux was supplied >>with 4Gb of ram (which if confirm at boot prompt) but Linux only see 2Gb. >> >>It is a dual cpu machine, is that 1/2 ram dedicated to 1 cpu and the other >>1/2 to the 2d cpu? > > > Unlikely. As I recall, the N4k diagram looks like this: > > <-PCI-> Elroy <-Ropes\ PA <-+-> PA PA <-+-> PA /Ropes-> Elroy > <-PCI-> Elroy <-Ropes-\ DEW RAM DEW /-Ropes-> Elroy > <-PCI-> Elroy <-Ropes--> IKE <-Merced-> Stretch <-Merced-> IKE <--Ropes-> Elroy > <-PCI-> Elroy <-Ropes-/ DEW RAM DEW \-Ropes-> Elroy > <-PCI-> Elroy <-Ropes/ PA <-+-> PA PA <-+-> PA \Ropes-> Elroy > > So the RAM is uniformly-accessible from all CPUs, but the IO is not. That is also what I believe to have understood from our previous talk about N Stretch mmu (but I am never sure to well undertand, thanks to confirm) > > If you look at pat_memconfig() in arch/parisc/kernel/inventory.c, you'll > see how we try to figure out what memory ranges are in the machine. > Want to try debugging that, see what's being reported by firmware? > I will try. Many thanks, Joel