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=-0.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 750936ae for ; Thu, 28 Jun 2018 16:59:44 +0000 (UTC) Received: by minnie.tuhs.org (Postfix, from userid 112) id 7E1ADA1851; Fri, 29 Jun 2018 02:59:43 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id A1340A1816; Fri, 29 Jun 2018 02:59:33 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b=pu6x1A7h; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id 3E78CA1816; Fri, 29 Jun 2018 02:59:31 +1000 (AEST) Received: from mail-lj1-f172.google.com (mail-lj1-f172.google.com [209.85.208.172]) by minnie.tuhs.org (Postfix) with ESMTPS id 8A2A39EDF1 for ; Fri, 29 Jun 2018 02:59:30 +1000 (AEST) Received: by mail-lj1-f172.google.com with SMTP id k20-v6so5072755ljk.9 for ; Thu, 28 Jun 2018 09:59:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=xxwOjm4YCxn3LA3P2ds9QHqpitLFmegwDRniHZMgI80=; b=pu6x1A7hpgyc7Q8B2yS7Z2+Qft7kvreWfCmpv+/g9sIaI7NH5PET2Lseqy+HRgRbIA hrrqAP1Vd3kKdA9SOvwuGDd9hqa/oRDLJ39pOTrzazPA7ipqMkZXHEi9k/ItrHzOY2sC OeHI0Hy9bBfig/8ifiybdfAYzqciq7WAgzwoSFv/Wc4BVSzVTxzeFEWowTlB3ciCA13R KMLrjqyj8+f6In5ejrqBqyaaBDoYKC/Cv/YvYSbcM5G5BUfAa6O/sW7IVCYHjdBa2Pxr sagZmJz8KNz3UqOnQz35zfdbJy//BkE2ENjkmqU7zgrxY4oAEQ4ars79uwpVsC/8LiLF c1Dg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=xxwOjm4YCxn3LA3P2ds9QHqpitLFmegwDRniHZMgI80=; b=Bi8qcVma0WNaf/UL+YMCKz7QqLwEJ9W6nizUp4wySTYVt2BWuusMPMrght+v/aCYqC i0/FMuiOuqbZSUPFCJqvzT+DW0I+FUI2qx3bZZ7er5jKhiw2UAA8iR1sXHdCkcCuO2cl phXNMHiRYNEwveGsF60C4/qADG6AujQwQh0Rh1PtVFLJdgAkEh3jDovDeK3hG/k83b2j fS5G1VCNyznKsXvSW9LsQkV5z/PzE4+nbnO6Mcecax5+IvM7g3dWGP0RvTaUgEE+8/6z NrpAUFYUgbXdd0+HhO4hvhScGfp8EsBZ1VkV3tjQ/IpJV5dTJiWMrvRE3WpgoqsxnoW3 Zeew== X-Gm-Message-State: APt69E2kxVkKRJDJ8cQb+4MboTb6jl03ikSlH69rBbup9i1Ob6o7+Sdh UJbu4LkzdthdjM1bwfWR/CVcCc4DycFgLcxhySI= X-Google-Smtp-Source: AAOMgpdZuOIa4ULFSG9QdHxeWBQyrblKIXkCexSO9958kadQwQCIOfx8jitDqKHqNEIL0kUE07PM13FPoCiibUW4CcY= X-Received: by 2002:a2e:4619:: with SMTP id t25-v6mr2136344lja.68.1530205168944; Thu, 28 Jun 2018 09:59:28 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a2e:5c81:0:0:0:0:0 with HTTP; Thu, 28 Jun 2018 09:59:28 -0700 (PDT) In-Reply-To: <79022674-0FFA-4B1B-8A27-4C403D51540E@tfeb.org> References: <81277CC3-3C4A-49B8-8720-CFAD22BB28F8@bitblocks.com> <20180628141538.GB663@thunk.org> <20180628144017.GB21688@mcvoy.com> <20180628105538.65f82615@jabberwock.cb.piermont.com> <20180628145825.GE21688@mcvoy.com> <2B710879-7659-47A4-AA86-03F232F7B78B@tfeb.org> <20180628160202.GF21688@mcvoy.com> <79022674-0FFA-4B1B-8A27-4C403D51540E@tfeb.org> From: Paul Winalski Date: Thu, 28 Jun 2018 12:59:28 -0400 Message-ID: To: tuhs@minnie.tuhs.org Content-Type: text/plain; charset="UTF-8" Subject: Re: [TUHS] PDP-11 legacy, C, and modern architectures 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" n re modern architectures, admiral Grace Hopper gave a talk at DEC's Nashua software development plant ca. 1982 on the future of computer architecture. She predicted the modern multi-core situation. As she put it, if you were a carter and had to haul double the load in your cart, you wouldn't breed bigger a horse twice as big--you'd hook up a team of horses. Another problem with solving problems fast is I/O bandwidth. Much of digital audio file, for example, is an embarrassingly parallel problem. But no matter how many cores you throw at the problem, and no matter how fast they are, the time it takes to process the audio file is limited by how fast you can get the original off the disk and the modified file back onto the disk. Or main memory, for that matter. Relative to the processor speed, a cache miss takes an eternity to resolve. Get your cache management wrong and your program ends up running an order of magnitude slower. It's a throwback to the situation in the 1960s, where compute speeds were comparable to main memory speeds, but vastly higher than the I/O transmission rates to disk and tape. Only now first-level cache is the new "main memory", and for practical purposes main memory is a slow storage medium. -Paul W.