Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267482AbUIPEu0 (ORCPT ); Thu, 16 Sep 2004 00:50:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267469AbUIPEu0 (ORCPT ); Thu, 16 Sep 2004 00:50:26 -0400 Received: from merkurneu.hrz.uni-giessen.de ([134.176.2.3]:7134 "EHLO merkurneu.hrz.uni-giessen.de") by vger.kernel.org with ESMTP id S267482AbUIPEta (ORCPT ); Thu, 16 Sep 2004 00:49:30 -0400 Date: Thu, 16 Sep 2004 14:48:58 +1000 (EST) From: Sergei Haller X-X-Sender: gc1007@magvis2.maths.usyd.edu.au To: linux-kernel@vger.kernel.org Subject: lost memory on a 4GB amd64 Message-Id: Organization: University of Giessen * Germany MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-HRZ-JLUG-MailScanner-Information: Passed JLUG virus check X-HRZ-JLUG-MailScanner: Found to be clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2747 Lines: 67 Hello, A friend of mine has a new Opteron based machine (Tyan Tiger K8W with two Opteron 24?) and 4GB main memory. the problem is that about 512 MB of that memory is lost (AGP aperture and stuff). Although everything is perfect otherwise. As far as I understand, all the PCI/AGP hardware uses the top end of the 4GB address range to access their memory and there is just an "overlapping" of the addresses. thus only the remaining 3.5 GB are available. Now there is an option in the BIOS called "Adjust Memory" which puts a certain amount of memory (several choices between 64MB and 2GB) above the 4GB address range. I tried the 2GB setting which results in 2GB main memory at addresses 0-2GB and 2GB memory at addresses 4GB-6GB. the problem is that the kernel (2.6.3-9mdksmp and vanilla 2.6.8.1) crashes if this option is enabled as soon as some memory expensive program is run (e.g. X) I've seen some postings on the net talking about some "kernel patch" for some "memory split", but nothing more specific. Do I just need a certain patch to get it working or is there more to it? BTW, the memory map displayed at boot is BIOS-e820: 0000000000000000 - 000000000009fc00 (usable) BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved) BIOS-e820: 0000000000100000 - 00000000d3ff0000 (usable) BIOS-e820: 00000000d3ff0000 - 00000000d3fff000 (ACPI data) BIOS-e820: 00000000d3fff000 - 00000000d4000000 (ACPI NVS) BIOS-e820: 00000000ff780000 - 0000000100000000 (reserved) if I leave the 4GB memory in one chunk and BIOS-e820: 0000000000000000 - 000000000009fc00 (usable) BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved) BIOS-e820: 0000000000100000 - 000000007fff0000 (usable) BIOS-e820: 000000007fff0000 - 000000007ffff000 (ACPI data) BIOS-e820: 000000007ffff000 - 0000000080000000 (ACPI NVS) BIOS-e820: 00000000ff780000 - 0000000100000000 (reserved) BIOS-e820: 0000000100000000 - 0000000180000000 (usable) if I enable the "adjust memory" option and split the memory in two 2GB blocks. Thanks in advance, Sergei -- -------------------------------------------------------------------- -?) eMail: Sergei.Haller@math.uni-giessen.de /\\ -------------------------------------------------------------------- _\_V Be careful of reading health books, you might die of a misprint. -- Mark Twain - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/