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=-0.8 required=5.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FROM,HTML_MESSAGE,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 22947 invoked from network); 15 Dec 2022 18:08:06 -0000 Received: from minnie.tuhs.org (50.116.15.146) by inbox.vuxu.org with ESMTPUTF8; 15 Dec 2022 18:08:06 -0000 Received: from minnie.tuhs.org (localhost [IPv6:::1]) by minnie.tuhs.org (Postfix) with ESMTP id D12BE4239A; Fri, 16 Dec 2022 04:07:58 +1000 (AEST) Received: from mail-oa1-f45.google.com (mail-oa1-f45.google.com [209.85.160.45]) by minnie.tuhs.org (Postfix) with ESMTPS id A463542399 for ; Fri, 16 Dec 2022 04:07:48 +1000 (AEST) Received: by mail-oa1-f45.google.com with SMTP id 586e51a60fabf-14455716674so255737fac.7 for ; Thu, 15 Dec 2022 10:07:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=6taAjdyr1zrrCEXIPp9a/qIBqMzII5rnZELmPkGL5Gc=; b=GNUQnSbs1ty43vGYVj7yMBoqM3sofmTVvDmDb6CXG2FZuDEXqOnpezpIPDEKtGN9EO ks/dPQJW0BTuHvRbDzlyHq9HRu1lG6Vs7Lt5tof73fOYbBHzKqxxKi9KBVPxKEjECCQm +FI1X0Qy+6x53f53svmYaRx3XIQB5A/MpZ2NFbzdGPX4wzEo9QB4V9zGEGbo8bR9Ycv5 cd77hvY2lP8DYrZ1Nv2Pw0EtaB1d5Fl1N5JWoFtWPBFRzfTcPs1OPPGRRU+1RiaTLJos X8s2mf3EgS2+vkQC5yZZuYdFxUKmxz85CFTrEHTfgTohV4X9LIe3BRFA+P4faTL2n9V9 8INw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=6taAjdyr1zrrCEXIPp9a/qIBqMzII5rnZELmPkGL5Gc=; b=3UFjJGvatnYORqMXiryiJ56xhECwzWM4X3SJN08uuCfP34wZANVHJqBJmrQGahw1qc 4a2a4hIJY0rA+JOOEMUoFddX3eOhkmOR8IdxGV8x64O0+bqznPO3p0fC9sq7OjKA9Bkx CCfJEt6NlF+w54YAK09XE/bn7EvWMj0I9qgKQYngI/kBQhg+emb0Nv0+rO+b7Cks4zbA aO7Y8v0pi5toAklTXlUKnmyht0qRnCQBELw+acK2xOltS1wZrwmgmGAxmapKy7AOrglj 5InFcIvQjFSSy6EBUksiMpNDfAw6MplGfyAaWbg9kKORET1Qiu9Nl48weZyF9eSCZ2fj geAw== X-Gm-Message-State: AFqh2koOT3U+1NnKnSTBurz0MMJHPyN/Q6luX0U3tXlN53LwhT49QReK /WO2eq3LwQEEG1EEI2tI/tkijC+6M+0eafqjAeVeOsB4ur8= X-Google-Smtp-Source: AMrXdXtzvk/3YJjMVzXgHx1YHKSBywwFFu5ApptyiaSUOlw30dIucFH3MKp119J0tHoRtFLyWjScr80eTafRpG+YbJc= X-Received: by 2002:a05:6870:fd94:b0:148:451:3b81 with SMTP id ma20-20020a056870fd9400b0014804513b81mr748429oab.175.1671127607601; Thu, 15 Dec 2022 10:06:47 -0800 (PST) MIME-Version: 1.0 References: <202212131431.2BDEVCls018959@freefriends.org> In-Reply-To: From: Marc Donner Date: Thu, 15 Dec 2022 13:06:36 -0500 Message-ID: To: Douglas McIlroy Content-Type: multipart/alternative; boundary="0000000000006cf2be05efe1b74c" Message-ID-Hash: 6O3S6PG5B7TH5B3K6MHFDGDNMWVZHWPF X-Message-ID-Hash: 6O3S6PG5B7TH5B3K6MHFDGDNMWVZHWPF X-MailFrom: marc.donner@gmail.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-tuhs.tuhs.org-0; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: tuhs@tuhs.org X-Mailman-Version: 3.3.6b1 Precedence: list Subject: [TUHS] Re: Clever code List-Id: The Unix Heritage Society mailing list Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: --0000000000006cf2be05efe1b74c Content-Type: text/plain; charset="UTF-8" Further on delay line storage: Physically one of the most common ones was a cylinder of liquid mercury. There was a device at one end for introducing pressure waves into the mercury (think loudspeaker) and a device at the other end for measuring the pressure waves arriving (think microphone). The pulses that came off the microphone end were then fed back to the loudspeaker end, after being cleaned up. ===== nygeek.net mindthegapdialogs.com/home On Tue, Dec 13, 2022 at 10:12 AM Douglas McIlroy < douglas.mcilroy@dartmouth.edu> wrote: > A delay line is logically like a drum, with circulating data that is > accessible only at one point on the circle. A delay line was > effectively a linear channel along which a train of data pulses was > sent. Pulses received at the far end were reshaped electronically. and > reinjected at the sending end. One kind of delay line was a mercury > column that carried acoustic pulses.. The PB 250 delay line was > magnetostrictive (a technology I know nothing about). > > If instruction timing is known, then the next instruction to appear is > predictable. The only caveat is that instruction times should not be > data-dependent. You can lay out sequential code along the circle as > long as no instruction steps on one already placed. When that happens > you must switch modes to jump to an open spot, or perhaps insert nops > to jiggle the layout. > > Doug > > On Tue, Dec 13, 2022 at 9:31 AM wrote: > > > > Douglas McIlroy wrote: > > > > > Apropos of accessing rotating storage, John Kelly used to describe the > > > Packard-Bell 250, which had a delay-line memory, as a machine where > > > addresses refer to time rather than space. > > > > > > The PB 250 had two instruction-sequencing modes. In one mode, each > > > instruction included the address of its successor. In the other mode, > > > whatever popped out the delay line when the current instruction > > > completed would be executed next. > > > > > > Doug > > > > For us (relative) youngsters, can you explain some more how delay > > line memory worked? The second mode you describe sounds like it > > would be impossible to use if you wanted repeatable, reproducible > > runs of your program. > > > > Thanks, > > > > Arnold > --0000000000006cf2be05efe1b74c Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Further on delay line storage:

Physically one of the most common ones was a cylinder= of liquid mercury.=C2=A0 There was a device at one end for introducing pre= ssure waves into the mercury (think loudspeaker) and a device at the other = end for measuring the pressure waves arriving (think microphone).=C2=A0 The= pulses that came off the microphone end were then fed back to the loudspea= ker end, after being cleaned up.

On Tue, = Dec 13, 2022 at 10:12 AM Douglas McIlroy <douglas.mcilroy@dartmouth.edu> wrote:
A delay line is logically l= ike a drum, with circulating data that is
accessible only at one point on the circle. A delay line was
effectively a linear channel along which a train of data pulses was
sent. Pulses received at the far end were reshaped electronically. and
reinjected at the sending end. One kind of delay line was a mercury
column that carried acoustic pulses.. The PB 250 delay line was
magnetostrictive (a technology I know nothing about).

If instruction timing is known, then the next instruction to appear is
predictable. The only caveat is that instruction times should not be
data-dependent. You can lay out sequential code along the circle as
long as no instruction steps on one already placed. When that happens
you must switch modes to jump to an open spot, or perhaps insert nops
to jiggle the layout.

Doug

On Tue, Dec 13, 2022 at 9:31 AM <arnold@skeeve.com> wrote:
>
> Douglas McIlroy <douglas.mcilroy@dartmouth.edu> wrote:
>
> > Apropos of accessing rotating storage, John Kelly used to describ= e the
> > Packard-Bell 250, which had a delay-line memory, as a machine whe= re
> > addresses refer to time rather than space.
> >
> > The PB 250 had two instruction-sequencing modes. In one mode, eac= h
> > instruction included the address of its successor. In the other m= ode,
> > whatever popped out the delay line when the current instruction > > completed would be executed next.
> >
> > Doug
>
> For us (relative) youngsters, can you explain some more how delay
> line memory worked? The second mode you describe sounds like it
> would be impossible to use if you wanted repeatable, reproducible
> runs of your program.
>
> Thanks,
>
> Arnold
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