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=MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 6913 invoked from network); 13 Dec 2022 15:34:43 -0000 Received: from minnie.tuhs.org (50.116.15.146) by inbox.vuxu.org with ESMTPUTF8; 13 Dec 2022 15:34:43 -0000 Received: from minnie.tuhs.org (localhost [IPv6:::1]) by minnie.tuhs.org (Postfix) with ESMTP id C4395423D6; Wed, 14 Dec 2022 01:34:37 +1000 (AEST) Received: from vmail1.sentex.ca (vmail1.sentex.ca [64.7.153.19]) by minnie.tuhs.org (Postfix) with ESMTPS id C6AD9423CD for ; Wed, 14 Dec 2022 01:34:32 +1000 (AEST) Received: (Haraka outbound); Tue, 13 Dec 2022 10:34:31 -0500 Authentication-Results: vmail1.sentex.ca; auth=pass (plain) Received: from [10.0.1.25] (198.27.14-65.ip.mltn.standardbroadband.ca [198.27.14.65]) by vmail1.sentex.ca (Haraka/2.8.25) with ESMTPSA id 84B6092D-FEF2-492B-AD47-E8E2A95AAC76.1 envelope-from (authenticated bits=0) (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256); Tue, 13 Dec 2022 10:34:31 -0500 Message-ID: <206fc6bb-cb58-eb9b-ab4d-b472547aa890@riddermarkfarm.ca> Date: Tue, 13 Dec 2022 10:34:29 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Content-Language: en-CA To: tuhs@tuhs.org References: <202212131431.2BDEVCls018959@freefriends.org> From: Stuff Received In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Haraka-GeoIP: NA, CA, ON, Georgetown, 40km Message-ID-Hash: BMN4F2RDKYECNIOHNICZO7SMMWWTYPW7 X-Message-ID-Hash: BMN4F2RDKYECNIOHNICZO7SMMWWTYPW7 X-MailFrom: stuff@riddermarkfarm.ca 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 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: On 2022-12-13 10:10, Douglas McIlroy 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. I had always thought of a delay line as a precursor to a register (or stack) for storing intermediate results. Is this not an accurate way of thinking about it? N. > 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