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=-1.0 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, HTML_MESSAGE,MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 3882 invoked from network); 15 Aug 2020 02:49:06 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 15 Aug 2020 02:49:06 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 8BC019B6B3; Sat, 15 Aug 2020 12:49:03 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id D84D69B5EC; Sat, 15 Aug 2020 12:48:16 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=pass (2048-bit key; unprotected) header.d=bsdimp-com.20150623.gappssmtp.com header.i=@bsdimp-com.20150623.gappssmtp.com header.b="kAjIGVLc"; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id 6167C9B5EC; Sat, 15 Aug 2020 12:48:12 +1000 (AEST) Received: from mail-qt1-f196.google.com (mail-qt1-f196.google.com [209.85.160.196]) by minnie.tuhs.org (Postfix) with ESMTPS id 718339B5D7 for ; Sat, 15 Aug 2020 12:48:10 +1000 (AEST) Received: by mail-qt1-f196.google.com with SMTP id o22so8417690qtt.13 for ; Fri, 14 Aug 2020 19:48:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=TAxyAnguhdJrqEz+zQdTClyCRtvxRzBPp6xf3nPX6z4=; b=kAjIGVLcVPp5jGAtDQoZ0HBOD6SOhBI6wuoBmn2F1gxg7oZJjs16GfvOsOfbKV5GvQ oPXysq31TqW4cHzNswZFGfHTaQ7Bc3c8u6l3fYEDvu608J+zEFykpPusZwJg0fwFKJlG Z5qYniNYIpJRNBsOJdiEOeMbLvuGb1YcwZY8k6Li8h6Pq5s+tgnBCR++gq0iMthVvKHP Fux3uvwfnFOj/snLoitodqsKSzWI2zFHkQiW4s1RyDqcrawCDcFuaSfBiVbE0HkLV7RY jF2YJF8jSHove+bnkWhMHpYZx4w0CdEW2d06mEl8W4uG3nOCutERAn9N4tmEIZTnKcL/ qIvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=TAxyAnguhdJrqEz+zQdTClyCRtvxRzBPp6xf3nPX6z4=; b=n2MXd9UlE8SdO+9Dhw4i86fBnkkrz+HLibeaDaH6jSTihCklKUFOtsoTVvqT1DEFFd iHYqpyi0FB29E5b9lnAhJzWh6Mmf7VrRldGeAZHmdo9aoUOZ3jeXP/daVaBf0UyfLAOJ 2Jjrn+O+Jguumpt3L5UBXmKYbNJPef334w7Y9H6EBdZet7BREiLm+MbQqHH2qVOwVh+Z YmQWJk8t8iPVUFymCyzdvXbjbgfTbkJPWtFRjxnPT45C9FVmj3tSkIGmN9WDKk6aqyhI OJoaM5m251CA2YkifejDypROufL2fxei/LTX4a5fTv6LEtoNgyv0Kbv0ze5fvUqSvcIu gwwQ== X-Gm-Message-State: AOAM531vV30FmD11TDq6RyQPNU3WqdvKeoXBDUNIRp9H0Wrur9wwU+6E 3PIJIaN4U46dZCp71t+MuDUVr0wWalIc/CzgnasuCMlYqKU= X-Google-Smtp-Source: ABdhPJypQKlLyf0yWNExm2+FVbtHwEKGK6eIhlax8ZC2aShn7v7FsuIi9OOfcXJvWAKWbTEmOAb/8jZshJFlwpf22lo= X-Received: by 2002:ac8:7a66:: with SMTP id w6mr4863359qtt.242.1597459689143; Fri, 14 Aug 2020 19:48:09 -0700 (PDT) MIME-Version: 1.0 References: <202008141739.07EHdn2U1381389@darkstar.fourwinds.com> <4F69D0BB-C6C8-443C-A5A2-0F0C1E5578B0@cfcl.com> <20200815012003.GQ32735@mcvoy.com> In-Reply-To: From: Warner Losh Date: Fri, 14 Aug 2020 20:47:56 -0600 Message-ID: To: Dave Horsfall Content-Type: multipart/alternative; boundary="0000000000005094ab05ace19108" Subject: Re: [TUHS] A/UX [was Linux is on-topic] 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: , Cc: The Eunuchs Hysterical Society Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" --0000000000005094ab05ace19108 Content-Type: text/plain; charset="UTF-8" On Fri, Aug 14, 2020, 8:09 PM Dave Horsfall wrote: > On Fri, 14 Aug 2020, Larry McVoy wrote: > > > I'm sure everyone here knows this, but the Cray 1 (I think, the one that > > had what looked like a circular bench seat around the bottom) was > > designed like that because the clock was at the center and the clock > > signal went to all the boards and was right because all the clock lines > > to the boards were the same length. > > Yep, timing was everything in those days (and I'm still amazed at the > people who believe that electricity moves at the speed of light). > > Wasn't it Grace Hopper who used to demonstrate a nanosecond by holding up > a foot of wire? > Yes. A nanosecond is just over a foot in copper... I used to do high precision timing and we used to make cables specific lengths to bring the on time point of different parts of the signal distribution system into alignment... you could also see how bands or kinks in the cables moved the on time point... Warner -- Dave > --0000000000005094ab05ace19108 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Fri, Aug 14, 2020, 8:09 PM Dave Horsfall <dave@ho= rsfall.org> wrote:
On Fri, = 14 Aug 2020, Larry McVoy wrote:

> I'm sure everyone here knows this, but the Cray 1 (I think, the on= e that
> had what looked like a circular bench seat around the bottom) was
> designed like that because the clock was at the center and the clock <= br> > signal went to all the boards and was right because all the clock line= s
> to the boards were the same length.

Yep, timing was everything in those days (and I'm still amazed at the <= br> people who believe that electricity moves at the speed of light).

Wasn't it Grace Hopper who used to demonstrate a nanosecond by holding = up
a foot of wire?

Yes. A nanosecond is just over a foot in copper...=C2=A0 I u= sed to do high precision timing and we used to make cables specific lengths= to bring the on time point of different parts of the signal distribution s= ystem into alignment... you could also see how bands or kinks in the cables= moved the on time point...

Warner

-- Dave
--0000000000005094ab05ace19108--