From owner-freebsd-current@FreeBSD.ORG Thu Jan 22 00:43:07 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4698016A4CE for ; Thu, 22 Jan 2004 00:43:07 -0800 (PST) Received: from cirb503493.alcatel.com.au (c211-30-75-229.belrs2.nsw.optusnet.com.au [211.30.75.229]) by mx1.FreeBSD.org (Postfix) with ESMTP id B306343D2D for ; Thu, 22 Jan 2004 00:43:04 -0800 (PST) (envelope-from PeterJeremy@optushome.com.au) Received: from cirb503493.alcatel.com.au (localhost.alcatel.com.au [127.0.0.1])i0M8gre3006859; Thu, 22 Jan 2004 19:42:53 +1100 (EST) (envelope-from jeremyp@cirb503493.alcatel.com.au) Received: (from jeremyp@localhost)i0M8gqLf006858; Thu, 22 Jan 2004 19:42:52 +1100 (EST) (envelope-from jeremyp) Date: Thu, 22 Jan 2004 19:42:52 +1100 From: Peter Jeremy To: Thomas David Rivers Message-ID: <20040122084252.GG908@cirb503493.alcatel.com.au> References: <14141.1074670873@critter.freebsd.dk> <200401211141.i0LBfnp57845@lakes.dignus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200401211141.i0LBfnp57845@lakes.dignus.com> User-Agent: Mutt/1.4.1i cc: phk@phk.freebsd.dk cc: current@freebsd.org Subject: Re: historical stuff in math(3) X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 22 Jan 2004 08:43:07 -0000 On Wed, Jan 21, 2004 at 06:41:49AM -0500, Thomas David Rivers wrote: >> Isn't all the vax-D format related stuff math(3) getting pretty old ? > > It's very similar to the IBM mainframe format. So, a port > of FreeBSD to the IBM mainframe could still use it. (The VAX > format was just a copy of the IBM one with an extra precision bit > thrown in every now-and-then.) Not really. The IBM S/360 uses base-16 whereas virtually everyone else (including VAX) uses binary. The S/360 double precision format has a 14-digit (56-bit) fraction (no implicit digit), a fraction sign and a 7-bit signed exponent. The VAX-D documentation in math(3) is totally irrelevant to the S/360. Any serious math library would need significant re-work to handle the increased range and reduced/variable precision. Someone else mentioned the Alpha - VAX-format FP is specified in the architecture to simplify migration from the VAX. The early chips included it in hardware - do the recent chips still include it? > But - even the mainframe has an available/alternate IEEE format now, > and the mainframe version of gcc uses that... I think this must be new in the S/390. It's definitely not part of the S/360 or S/370 families and I don't believe it existed on the 30xx or 43xx families. Peter