From owner-freebsd-arm@FreeBSD.ORG Sun Nov 12 23:53:15 2006 Return-Path: X-Original-To: arm@freebsd.org 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 3302C16A40F; Sun, 12 Nov 2006 23:53:15 +0000 (UTC) (envelope-from nick@flirble.org) Received: from plum.flirble.org (plum.flirble.org [195.40.6.20]) by mx1.FreeBSD.org (Postfix) with ESMTP id C784A43D53; Sun, 12 Nov 2006 23:53:13 +0000 (GMT) (envelope-from nick@flirble.org) Received: from nick by plum.flirble.org with local (Exim 4.43) id 1GjP8S-000MHd-UN; Sun, 12 Nov 2006 23:53:12 +0000 Date: Sun, 12 Nov 2006 23:53:12 +0000 From: Nicholas Clark To: Olivier Houchard Message-ID: <20061112235312.GV6501@plum.flirble.org> Mail-Followup-To: Olivier Houchard , Joseph Koshy , Giorgos Keramidas , arm@freebsd.org References: <20061112133929.9194773068@freebsd-current.sentex.ca> <20061112140010.GA47660@rambler-co.ru> <20061112144230.GC2331@kobe.laptop> <20061112145151.GC49703@rambler-co.ru> <20061112151150.GA2988@kobe.laptop> <84dead720611120758r4f1cc6e8l8ca4432ba56f3f7f@mail.gmail.com> <20061112170711.GQ6501@plum.flirble.org> <20061112233434.GA12739@ci0.org> <20061112232742.GU6501@plum.flirble.org> <20061112234412.GA12998@ci0.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061112234412.GA12998@ci0.org> User-Agent: Mutt/1.3.25i X-Organisation: Tetrachloromethane Sender: Nicholas Clark Cc: arm@freebsd.org, Giorgos Keramidas , Joseph Koshy Subject: Re: [head tinderbox] failure on arm/arm X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Porting FreeBSD to the StrongARM Processor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 12 Nov 2006 23:53:15 -0000 On Mon, Nov 13, 2006 at 12:44:12AM +0100, Olivier Houchard wrote: > On Sun, Nov 12, 2006 at 11:27:42PM +0000, Nicholas Clark wrote: > > On Mon, Nov 13, 2006 at 12:34:34AM +0100, Olivier Houchard wrote: > > > > > No, we're not using the mixed endian IEEE 64bits representation. We're > > > defaulting to softfloat VFP. What would be te point of switching ? > > > > >From my limited understanding of these things (mostly observing on the > > ARM Linux lists) absolutely none. The mixed endian IEEE representation > > is a complete pain, I'm unaware of any reason why it was chosen over a > > conventional little endian representation (probably back some time in > > 1987). > > > > I thought so :) > I think FPA is used for historical reasons, because that's what some older > arm cpus used when they had a FPU. And of course using a kernel FPE was a > great idea for linux too. But I think that the FPA (the external floating point unit) only was only actually produced to used with the 25 Mhz ARM 3s (*), which I think was 1990 or so, which I think would be the first time that mixed endian layout was set in silicon. But the mixed endian layout would have had to have been chosen before RISC OS 2 shipped in 1989, as it had bundled applications written in C, which uses the (emulated) floating point instructions. Hence as far as I know there was no hardware reason to choose that layout - hardware came later. Nicholas Clark * because at the time I upgraded my parents' Archimedes to an ARM 3, I asked about this, and the 30 Mhz CPU-on-a-daughterboards then available would not suitable for adding an FPA, not that it mattered, as the run of FPAs was now all sold)