From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from colo.lackof.org (colo.lackof.org [198.49.126.79]) by dsl2.external.hp.com (Postfix) with ESMTP id 59666488A for ; Sat, 21 Feb 2004 22:49:43 -0700 (MST) Date: Sat, 21 Feb 2004 22:49:42 -0700 From: Grant Grundler To: Matthew Wilcox Subject: Re: [parisc-linux] Linux only see 2Gb of ram of N4k Message-ID: <20040222054942.GD30849@colo.lackof.org> References: <402A4CA500006EA3@ocpmta2.freegates.net> <20040220182140.GC11824@parcelfarce.linux.theplanet.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20040220182140.GC11824@parcelfarce.linux.theplanet.co.uk> Cc: parisc-linux@lists.parisc-linux.org List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Feb 20, 2004 at 06:21:40PM +0000, Matthew Wilcox wrote: > Unlikely. As I recall, the N4k diagram looks like this: Beautiful diagram! (I'm saving that one) And I confirmed it is correct in case anyone had doubts. (I did) > So the RAM is uniformly-accessible from all CPUs, but the IO is not. I don't think there is much penalty for CPU's to access MMIO space on "the other side". MMIO reads are so expensive anyway, I'd doubt it would make that much difference. > 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'm pretty sure it will look like this: RAM Phys Address 0-2GB -> 0-2GB -> 2-4GB I/O Space (mostly PCI MMIO) 2-4GB -> 4-6GB (courtesy of the memory controller) The N-class was the first box which has an I/O hole from 2-4GB physical address range. I hope Joel will be able to confirm this. If not, I likely have documentation to confirm this. grant