From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: tuhs-bounces@minnie.tuhs.org X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.1 Received: from minnie.tuhs.org (minnie.tuhs.org [45.79.103.53]) by inbox.vuxu.org (OpenSMTPD) with ESMTP id 2aa0f26a for ; Thu, 21 Jun 2018 13:46:54 +0000 (UTC) Received: by minnie.tuhs.org (Postfix, from userid 112) id 00411A17C4; Thu, 21 Jun 2018 23:46:53 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 1E7069EDE7; Thu, 21 Jun 2018 23:46:29 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id C4B5D9EDE7; Thu, 21 Jun 2018 23:46:24 +1000 (AEST) Received: from mail.cs.Dartmouth.EDU (mail.cs.dartmouth.edu [129.170.212.100]) by minnie.tuhs.org (Postfix) with ESMTPS id 1A6889EDE5 for ; Thu, 21 Jun 2018 23:46:22 +1000 (AEST) Received: from tahoe.cs.Dartmouth.EDU (tahoe.cs.dartmouth.edu [129.170.212.20]) by mail.cs.Dartmouth.EDU (8.15.2/8.15.2) with ESMTPS id w5LDkJGo004259 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Thu, 21 Jun 2018 09:46:19 -0400 Received: from tahoe.cs.Dartmouth.EDU (localhost.localdomain [127.0.0.1]) by tahoe.cs.Dartmouth.EDU (8.15.2/8.14.3) with ESMTP id w5LDkJAW126946 for ; Thu, 21 Jun 2018 09:46:19 -0400 Received: (from doug@localhost) by tahoe.cs.Dartmouth.EDU (8.15.2/8.15.2/Submit) id w5LDkJJG126945 for tuhs@tuhs.org; Thu, 21 Jun 2018 09:46:19 -0400 From: Doug McIlroy Message-Id: <201806211346.w5LDkJJG126945@tahoe.cs.Dartmouth.EDU> Date: Thu, 21 Jun 2018 09:46:19 -0400 To: tuhs@tuhs.org User-Agent: Heirloom mailx 12.5 7/5/10 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: [TUHS] core X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.20 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" Tim Bradshaw wrote: "Making tube (valve) machines reliable was something originally sorted out by Tommy Flowers, who understood, and convinced people with some difficulty I think, that you could make a machine with one or two thousand valves (1,600 for Mk 1, 2,400 for Mk 2) reliable enough to use, and then produced ten or eleven Colossi from 1943 on which were used to great effect in. So by the time of Whirlwind it was presumably well-understood that this was possible." "Colossus: The Secrest of Bletchley Park's Codebreaking Computers" by Copeland et al has little to say about reliability. But one ex-operator remarks, "Often the machine broke down." Whether it was the (significant) mechanical part or the electronics that typically broke is unclear. Failures in a machine that's always doing the same thing are easier to detect quickly than failures in a mchine that has a varied load. Also the task at hand could fail for many other reasons (e.g. mistranscribed messages) so there was no presumption of correctness of results--that was determined by reading the decrypted messages. So I think it's a stretch to argue that reliability was known to be a manageable issue. Doug