From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750703AbWG2WWD (ORCPT ); Sat, 29 Jul 2006 18:22:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750711AbWG2WWD (ORCPT ); Sat, 29 Jul 2006 18:22:03 -0400 Received: from mx2.suse.de ([195.135.220.15]:27627 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S1750703AbWG2WWB (ORCPT ); Sat, 29 Jul 2006 18:22:01 -0400 To: Robert Hancock Cc: iforone , linux-kernel@vger.kernel.org Subject: Re: BIOS detects 4 GB RAM, but kernel does not References: <1153931278.034068.54630@h48g2000cwc.googlegroups.com> <1153933737.200164.160870@m73g2000cwd.googlegroups.com> <1154007393.940693.259680@i42g2000cwa.googlegroups.com> <1154112339.037481.119210@p79g2000cwp.googlegroups.com> <44CAC249.1010605@shaw.ca> From: Andi Kleen Date: 30 Jul 2006 00:21:59 +0200 In-Reply-To: <44CAC249.1010605@shaw.ca> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Robert Hancock writes: > Athlon 64/Opteron CPUs have support for moving this part of the RAM > above 4GB to allow it to be used. This is part of the CPU's on-die > memory controller so no special chipset support is needed. In cheap boards >3.5GB RAM configurations are usually not officially supported by the vendor (= not tested) and there are systems where it doesn't work when enabled in the BIOS (doesn't work = kernel crashes randomly when accessing bad memory ranges) I guess it's a subtle hint that above 3GB of RAM you should be using ECC DIMMs anyways, which need a more expensive workstation class board. -Andi