From owner-freebsd-current@FreeBSD.ORG Thu Jan 22 03:57:40 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 C6F4216A4CE for ; Thu, 22 Jan 2004 03:57:40 -0800 (PST) Received: from dignus.com (ip-64-32-254-102.dsl.iad.megapath.net [64.32.254.102]) by mx1.FreeBSD.org (Postfix) with ESMTP id 2ED4543D2D for ; Thu, 22 Jan 2004 03:57:39 -0800 (PST) (envelope-from rivers@dignus.com) Received: from lakes.dignus.com (lakes.dignus.com [10.0.0.3]) by dignus.com (8.12.8p1/8.12.8) with ESMTP id i0MBvPNZ014501; Thu, 22 Jan 2004 06:57:25 -0500 (EST) (envelope-from rivers@dignus.com) Received: (from rivers@localhost) by lakes.dignus.com (8.11.6/8.11.3) id i0MBugU62065; Thu, 22 Jan 2004 06:56:42 -0500 (EST) (envelope-from rivers) Date: Thu, 22 Jan 2004 06:56:42 -0500 (EST) From: Thomas David Rivers Message-Id: <200401221156.i0MBugU62065@lakes.dignus.com> To: PeterJeremy@optushome.com.au, rivers@dignus.com In-Reply-To: <20040122084252.GG908@cirb503493.alcatel.com.au> 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 11:57:40 -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. My bad... I thought the VAX code was base-16 as well. I could be confusing it with the Data General MV series... > > 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. Yes - new will ALS 1 (Architectural Level Set #1). If your OS/390 operating system is new enough (past 1992 I think?), it will emulate the new IEEE instructions if your hardware doesn't have them. Linux will do the same thing. The mainframe has evolved quite a lot since the 360. The new z/Series machines are serious 64-bit Linux contenders. But - I'm getting off-topic... - Dave R. - -- rivers@dignus.com Work: (919) 676-0847 Get your mainframe programming tools at http://www.dignus.com