From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267206AbUBMWVX (ORCPT ); Fri, 13 Feb 2004 17:21:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267251AbUBMWVX (ORCPT ); Fri, 13 Feb 2004 17:21:23 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.104]:47599 "EHLO e4.ny.us.ibm.com") by vger.kernel.org with ESMTP id S267206AbUBMWVV (ORCPT ); Fri, 13 Feb 2004 17:21:21 -0500 Date: Fri, 13 Feb 2004 14:18:54 -0800 From: "Martin J. Bligh" To: Matt Domsch cc: Sean Neakums , Nagy Tibor , xela@slit.de, mochel@osdl.org, bmoyle@mvista.com, orc@pell.chi.il.us, linux-kernel@vger.kernel.org Subject: Re: HIGHMEM Message-ID: <46620000.1076710734@flay> In-Reply-To: <20040213160909.A6102@lists.us.dell.com> References: <402CC114.8080100@dell633.otpefo.com> <6uvfmbktrj.fsf@zork.zork.net> <64200000.1076688313@[10.10.2.4]> <20040213160909.A6102@lists.us.dell.com> X-Mailer: Mulberry/2.1.2 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > On Fri, Feb 13, 2004 at 08:05:14AM -0800, Martin J. Bligh wrote: >> >> We have two Dell Poweredge servers, an older one (PowerEdge 6300) and a >> >> newer one (PowerEdge 6400). Both servers have 4GB RAM, but the Linux >> >> kernel uses about 500MB less memory in the newer machine. >> > >> > I may be talking through my hat, but I think that in this case you >> > need to select the option for support of 64G highmem. If I recall, >> > "4G highmem" refers not to the total amount to the memory, but to the >> > highest physical address that can be accessed. >> >> That's exactly correct. Whether the gain of 500MB of RAM is worth the >> overhead of PAE is another question ... but that's how to do it ;-) > > If the chipset and BIOS can't remap the physical RAM out of the > address space needed by the PCI devices and into PAE space, then PAE > doesn't buy you anything. You need chipset support for RAM remapping, > which doesn't exist on the servers mentioned. Ah, didn't realise you had a hardware problem as well ;-) M.