From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754218AbXFVBqg (ORCPT ); Thu, 21 Jun 2007 21:46:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753863AbXFVBqY (ORCPT ); Thu, 21 Jun 2007 21:46:24 -0400 Received: from terminus.zytor.com ([192.83.249.54]:47412 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753719AbXFVBqX (ORCPT ); Thu, 21 Jun 2007 21:46:23 -0400 Message-ID: <467B29DA.9040309@zytor.com> Date: Thu, 21 Jun 2007 18:46:02 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: Rene Herman CC: Bart Trojanowski , linux-kernel@vger.kernel.org Subject: Re: how to tell linux (on x86) to ignore 1M or memory References: <20070419141804.GO32620@jukie.net> <46290DED.80500@gmail.com> In-Reply-To: <46290DED.80500@gmail.com> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Rene Herman wrote: > On 04/19/2007 04:18 PM, Bart Trojanowski wrote: > >> I need to preserve some state from the bios before entering protected >> mode. For now I want to copy it into some ram accessible by >> real-mode, say the last megabyte visible in real-mode. >> >> What's the easiest way to have linux ignore the megabyte starting at 15M? > > Note that real-mode can only access the first megabyte (*) and not the > first 16. 16MB is the 16-bit protected mode (286) limit. > No, 16-bit protected mode (on 386+) is not limited to 16 MB. The main reason there is a 16 MB limit in some current systems is that ISA, and the ISA DMA controller only had 24 address lines. -hpa