From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 19 Feb 2001 17:08:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 19 Feb 2001 17:08:20 -0500 Received: from slc868.modem.xmission.com ([166.70.6.106]:7690 "EHLO flinx.biederman.org") by vger.kernel.org with ESMTP id ; Mon, 19 Feb 2001 17:08:16 -0500 To: Jeremy Jackson Cc: Jaswinder Singh , peterw@dascom.com.au, "Albert D. Cahalan" , linux-kernel@vger.kernel.org Subject: Re: Kernel executation from ROM In-Reply-To: <01e701c09a2a$21e789a0$bba6b3d0@Toshiba> <3A914E57.9990EB7C@sympatico.ca> From: ebiederm@xmission.com (Eric W. Biederman) Date: 19 Feb 2001 12:50:34 -0700 In-Reply-To: Jeremy Jackson's message of "Mon, 19 Feb 2001 11:48:23 -0500" Message-ID: User-Agent: Gnus/5.0803 (Gnus v5.8.3) Emacs/20.5 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jeremy Jackson writes: > Jaswinder Singh wrote: > > > Dear Sirs, > > > > Thanks for your help, > > > > I see . The biggest negative point of running kernel from ROM is that ROM > > speed is slow :( > > Also, the PCI specification forbids executing code from ROMs over the PCI bus. > The system BIOS in a PC is not on the PCI bus, bus, but everything else is. No it forbids executing boot roms that way, by a standard pc bios. The system BIOS in a PC is normally on the ISA bus which is reached across via the PCI bus with a PCI->ISA bridge. The thing is slow it really doesn't matter, all you need to do is enable caching on that area of the physical address space. You can't do this on the alpha currently but only because the alpha sucks that way. You can on practically everything else. As for ROM being slow on x86 you can enable the MTRR to speed things up. Usually though ROMs are at least as expensive as RAM, so it is pointless. Eric