From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Wed, 21 Jan 2004 22:38:00 +0000 (GMT) Received: from gateway-1237.mvista.com ([IPv6:::ffff:12.44.186.158]:58610 "EHLO orion.mvista.com") by linux-mips.org with ESMTP id ; Wed, 21 Jan 2004 22:38:00 +0000 Received: (from jsun@localhost) by orion.mvista.com (8.11.6/8.11.6) id i0LMbr430733; Wed, 21 Jan 2004 14:37:53 -0800 Date: Wed, 21 Jan 2004 14:37:53 -0800 From: Jun Sun To: Nils Larson Cc: linux-mips@linux-mips.org, jsun@mvista.com Subject: Re: How to add more memory? Message-ID: <20040121143753.C29705@mvista.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from nlarson@Crossroads.com on Wed, Jan 21, 2004 at 03:58:24PM -0600 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 4089 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: jsun@mvista.com Precedence: bulk X-list: linux-mips On Wed, Jan 21, 2004 at 03:58:24PM -0600, Nils Larson wrote: > Hi, > We currently have a mips platform running Linux with 256MB of > RAM starting at 0x8000_0000. We would like to add an additional > 1GB of RAM, maybe starting at 0x4000_0000, that would be used > for user apps (user virtual memory). The memory map is: > 0x8000_0000 - 256MB RAM > 0xA000_0000 - uncached version of the same 256MB > 0xB000_0000 - PCI memory windows. > This is a diskless setup booting from a ramdisk. > So, the (sort of newbie) questions are: > 1. How do we tell Linux to use the new memory? > 2. Is this feasible? > 3. Is there a better way to add more memory? > We need more space for user data. > Thanks, > Nils > People have done this before in 2.4 with CONFIG_HIGHMEM. See arch/mips/sibyte/cfe/setup.c for more details. However, if the CPU suffers from virtual aliasing problem, I think this won't work at all. I think that is pretty much only way to get more RAM in 32bit system. With 64bit kernel of course you don't have any problems at all. Jun