From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Smirl Subject: Re: Reading the EDID block for x86 machines Date: Mon, 17 Mar 2003 14:02:15 -0800 (PST) Sender: linux-fbdev-devel-admin@lists.sourceforge.net Message-ID: <20030317220215.49788.qmail@web14902.mail.yahoo.com> References: <1047933906.3668.18.camel@localhost.localdomain> Mime-Version: 1.0 Return-path: Received: from web14902.mail.yahoo.com ([216.136.225.54]) by sc8-sf-list1.sourceforge.net with smtp (Exim 3.31-VA-mm2 #1 (Debian)) id 18v2gS-0002WL-00 for ; Mon, 17 Mar 2003 14:02:16 -0800 In-Reply-To: <1047933906.3668.18.camel@localhost.localdomain> Errors-To: linux-fbdev-devel-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Id: List-Unsubscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Antonino Daplas Cc: Geert Uytterhoeven , James Simmons , Linux Fbdev development list The VBIOS should be position independent code and it will run at any 64K boundary. The PC bus spec simply says the video BIOS defaults to C000, it is not a requirement that it be located there. For example if you look at the aty128fb driver's find ROM routine your will notice that it is searching a broad address space for the ROM. I'm still not convinced that the memory at C000 is really hardware write protected, I think it is just RAM with a copy of the ROM in it. For example if I turn off BIOS shadowing my system will not boot. When debugging this I spent some time tracing into the ATI ROM and I was pretty sure that they are dependent on begin copied into RAM before begin run. Do you have a DOS floppy around? Just boot into DOS, start debug and see if you can change C000:0. If C000:0 is hardware write protected, there is nothing stopping the ROM from begin copied into 8000:0 or 9000:0 or whatever where there is guaranteed RAM. We would just need to temporarily get the kernel out of the way. ===== Jon Smirl jonsmirl@yahoo.com __________________________________________________ Do you Yahoo!? Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop! http://platinum.yahoo.com ------------------------------------------------------- This SF.net email is sponsored by:Crypto Challenge is now open! Get cracking and register here for some mind boggling fun and the chance of winning an Apple iPod: http://ads.sourceforge.net/cgi-bin/redirect.pl?thaw0031en