From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752047AbWG1RHz (ORCPT ); Fri, 28 Jul 2006 13:07:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752049AbWG1RHz (ORCPT ); Fri, 28 Jul 2006 13:07:55 -0400 Received: from shawidc-mo1.cg.shawcable.net ([24.71.223.10]:47995 "EHLO pd5mo1so.prod.shaw.ca") by vger.kernel.org with ESMTP id S1752047AbWG1RHy (ORCPT ); Fri, 28 Jul 2006 13:07:54 -0400 Date: Fri, 28 Jul 2006 11:06:08 -0600 From: Robert Hancock Subject: Re: BIOS detects 4 GB RAM, but kernel does not In-reply-to: To: Jan Engelhardt Cc: ravibt@gmail.com, linux-kernel Message-id: <44CA4400.5020005@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: <1153931278.034068.54630@h48g2000cwc.googlegroups.com> <44C79E56.2040603@shaw.ca> User-Agent: Thunderbird 1.5.0.4 (Windows/20060516) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jan Engelhardt wrote: >> Essentially I don't think there is much you can do about this on this board. >> The memory space starting at around 3.2GB is being used by the memory-mapped IO >> regions for the PCI and PCI Express devices and motherboard resources and >> therefore "covers up" the RAM in that part of the address space. The solution >> to this is for the system to remap the affected memory above the 4GB mark, >> which is possible with Athlon 64/Opteron CPUs and on some of the Intel server >> chipsets. However, I don't think any Intel desktop chipsets support this for >> some unfathomable reason. > > Maybe PAE can help? No.. it's not a matter of being unable to reach the address space, but the memory used by the IO regions is essentially overridden and unavailable to the kernel. PAE is not applicable on x86-64 anyway.. -- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/