From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 32333 invoked from network); 28 Sep 2020 17:42:04 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 28 Sep 2020 17:42:04 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 793CB9CEF3; Tue, 29 Sep 2020 03:41:57 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 8ADBF9CEB2; Tue, 29 Sep 2020 03:41:14 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=pass (2048-bit key; unprotected) header.d=papnet.eu header.i=@papnet.eu header.b="JxVfm+fj"; dkim=pass (2048-bit key; unprotected) header.d=messagingengine.com header.i=@messagingengine.com header.b="QbfF2nqS"; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id 43CAE9CEB2; Tue, 29 Sep 2020 03:41:11 +1000 (AEST) X-Greylist: delayed 307 seconds by postgrey-1.36 at minnie.tuhs.org; Tue, 29 Sep 2020 03:41:07 AEST Received: from out5-smtp.messagingengine.com (out5-smtp.messagingengine.com [66.111.4.29]) by minnie.tuhs.org (Postfix) with ESMTPS id 8032D9CE8C for ; Tue, 29 Sep 2020 03:41:07 +1000 (AEST) Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailout.nyi.internal (Postfix) with ESMTP id B6A7C5C019F for ; Mon, 28 Sep 2020 13:35:58 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute4.internal (MEProxy); Mon, 28 Sep 2020 13:35:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=papnet.eu; h= date:from:to:subject:message-id:references:mime-version :content-type:in-reply-to; s=fm2; bh=b3Gl1yUTkpqTyA0elPlBQ+nWQk9 5nzhx5fD73yngqmk=; b=JxVfm+fjKceFVI7ZzlcGhKl2S4ubLJnA4YPYrC5hdyO SdKFNBjh/4A3q5318DXyI8pnJR7j0N9SasPGmxBlS67hBVrmTr2BTzj9yqWuU/Kf +m/E7LjUM4V/FFXcnh084/foGfo2Y5FOT6Ws3OcE7mIs3E2qZVl5Zj8Yf59PX2ju THj2UdBF+paB+vHEDhUfqNU3r/lUi1WPnADQTeg6w7CSGSfTXL2bt1DCU+z9ZO0T EcQY3dVzQMQPbTj5yBqF4iwjIzDeDXgLmUY+v7k2cr6eR006NHWAStqvHXQLiBgt TiiT6gbhW/H8GdvlmNCezBuY02Gb1ui0a7Jow1bB20Q== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm3; bh=b3Gl1y UTkpqTyA0elPlBQ+nWQk95nzhx5fD73yngqmk=; b=QbfF2nqSQmU55G5zF0V8zL PkrVdt5e2JcYjYbNbEFkkG2BcTU7y66nH1ux8pqiP/eVKNXHGE4kXOLLcsbHP6rB cPDdO0UpcproJrrUFtVGhF6+AlxR7LjoOvs47BXqyEoezu5ux7Juujo+s8U/JDli TOuSqT7pUXHI2sqT/boUA/ERkDuvUzhcpAAa3UwzdpdSsArjp2M2dComRNyXLguL o0TyPViKGL9nUXoa+DkldULsUswAl2i8T35I/GrXdn6nn4BdOtpGXowdAjC312yU i2A+vPK5H0q9oODP+rxlNu7L6c0tPQCsVjbBxusgPwG45R4aHD5MDjzjKqAXsysw == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedujedrvdeigdelvdcutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecunecujfgurhepfffhvffukfhfgggtuggjfgesthdtre dttdervdenucfhrhhomheptehnghgvlhhoucfrrghpvghnhhhofhhfuceorggrphesphgr phhnvghtrdgvuheqnecuggftrfgrthhtvghrnhepvdfgvddugfeugfelledugfdtjeetvd dvueegleeggffgheeiffefleffhfehtedunecukfhppeejjedrudeluddrudduledrkedv necuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomheprggrph esphgrphhnvghtrdgvuh X-ME-Proxy: Received: from indra.papnet.eu (x4dbf7752.dyn.telefonica.de [77.191.119.82]) by mail.messagingengine.com (Postfix) with ESMTPA id 08EBB328005D for ; Mon, 28 Sep 2020 13:35:57 -0400 (EDT) Date: Mon, 28 Sep 2020 19:35:56 +0200 From: Angelo Papenhoff To: tuhs@tuhs.org Message-ID: <20200928173555.GA78180@indra.papnet.eu> References: <202009251419.08PEJPkV248911@coolidge.cs.dartmouth.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202009251419.08PEJPkV248911@coolidge.cs.dartmouth.edu> User-Agent: Mutt/1.6.0 (2016-04-01) Subject: Re: [TUHS] reviving a bit of WWB X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" On 25/09/20, Doug McIlroy wrote: > > Turing save us from 1-complement machines! > > Users of Whirlwind II were warned about the quirks of -0. > We were not warned, though, about integer divide with remainder 0. > The result of dividing 6 by 3, for example, was binary 1.111111... - > a valid answer when carried to infinity. Unfortunately, the > "fractional" part was dropped. > > Most people used Whirlwind for floating-point computation, and > blithely dismissed printed answers like 1.999999 as "roundoff > errors". It's funny that you mention that. I'm working on a verilog simulation of the Whirlwind I right now and I *just* came across this quirk. Now I'm really glad I remembered this mail of yours. Otherwise I might have spent some time trying to debug this non-bug. Thanks a lot! (The simulation is based on the description from 1947, so it doesn't describe the machine as it actually ran in the 50s. It would be great to have more material on its later life.) aap