From owner-freebsd-arm@FreeBSD.ORG Tue May 25 16:10:27 2004 Return-Path: Delivered-To: freebsd-arm@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9DEA516A4CE for ; Tue, 25 May 2004 16:10:27 -0700 (PDT) Received: from dong.ci0.org (cognet.ci0.org [80.65.224.102]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7447043D45 for ; Tue, 25 May 2004 16:10:26 -0700 (PDT) (envelope-from doginou@dong.ci0.org) Received: from dong.ci0.org (localhost.ci0.org [127.0.0.1]) by dong.ci0.org (8.12.11/8.12.11) with ESMTP id i4PNHox0012488; Wed, 26 May 2004 01:17:50 +0200 (CEST) (envelope-from doginou@dong.ci0.org) Received: (from doginou@localhost) by dong.ci0.org (8.12.11/8.12.11/Submit) id i4PNHoAQ012487; Wed, 26 May 2004 01:17:50 +0200 (CEST) (envelope-from doginou) Date: Wed, 26 May 2004 01:17:49 +0200 From: Olivier Houchard To: Morton Lin Message-ID: <20040525231749.GA12360@ci0.org> References: <003301c4420c$3391f220$4455608c@11091019701> <1085489504.31926.2.camel@mill.nexus.co.uk> <20040525130914.GA9944@ci0.org> <002301c44278$3f3eb740$c50a27ca@p3bf> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <002301c44278$3f3eb740$c50a27ca@p3bf> User-Agent: Mutt/1.4.1i cc: freebsd-arm@freebsd.org cc: Philip Blundell Subject: Re: I want to buy an ARM dev. board X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Porting FreeBSD to the StrongARM Processor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 May 2004 23:10:27 -0000 On Wed, May 26, 2004 at 12:49:15AM +0800, Morton Lin wrote: > Sure, ARM940T only had Memory Protection Unit, also {I | D}-cache. But I > thought > it can have some similar capabilities like an MCU which had MMU. (Of course, > for > FreeBSD/ARM, it's a lot of work / re-write to achieve that) > > IMHO, in modern embedded market, there were many MMUless MCUs used in > valuable field. Even those MCUs which had MMU, the EmbeddedOS/RTOS went > along with, didn't use their MMU functions. For example, uCLinux. There're > cost and > budget issues behind this situation. In low end application I think the > 32bits MCU like > the ARM7/9 series will be the main stream. In high end field, I think the > Intel XScale > (w/ MMU) will be the star. > > So, are we going to have two directions for the FreeBSD/ARM ? Is it possible > ? Can > anyone tell us how much effort do we need to take and how difficult if we > want to port > FreeBSD/ARM to a MMUless core/platform ? Or we just move toward the Intel > XScale > architecture ? > Well, it sounds like a huge amount of work, and I don't think FreeBSD is well suited for that kind of applications. Supporting MMUless cpus would require to either emulate the MMU, which I think would cost far to much, or to re-design the FreeBSD kernel to not rely on the virtual memory, and it wouldn't be FreeBSD anymore :-) Any suggestion would be welcome but I can't see any way to get FreeBSD to run on a MMU-less cpu without a major work. Cheers, Olivier