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=-1.1 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FROM,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 32222 invoked from network); 1 Dec 2021 16:45:29 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 1 Dec 2021 16:45:29 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 0F70F9CE1F; Thu, 2 Dec 2021 02:45:27 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 265089C78B; Thu, 2 Dec 2021 02:44:59 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="FNQUfIl5"; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id 2B3069C78B; Thu, 2 Dec 2021 02:42:30 +1000 (AEST) Received: from mail-oi1-f178.google.com (mail-oi1-f178.google.com [209.85.167.178]) by minnie.tuhs.org (Postfix) with ESMTPS id DBCB694502 for ; Thu, 2 Dec 2021 02:42:28 +1000 (AEST) Received: by mail-oi1-f178.google.com with SMTP id m6so49743112oim.2 for ; Wed, 01 Dec 2021 08:42:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=PpYZjEP26zVKjMwBNHpMtJjObqUy8yUZUmgf6pYuf4Q=; b=FNQUfIl5VFIenHlRJxTpqePiZDgpVurwd4KS/d/givY7GUj4z3rnsISmGE/cKAgRfU 3Oc+BCvL9j0vo4YIbZpPZDpYJ0q/UiWot583Ej90biLNpkwFgP7id90SF867pXmaccvl 6KJJ/qzwQqesl+3ADyQcgQVRjWdxKiMXP7sTm40iAboTgISJliIeigfG9ZJHkKmJXa3a 4GV3+Lfg4z/J/wA56F/rPNibynALW8WxAgrr5L1LrySQ4MRmuung22fdiXoljfWy7HnS 5PEvXQsjEG7Z8eK5MHT2tDkYSg1Itxolz0cwSFoGbh1rixudKUhVQD/Jw4iuODKz3DQv lTfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=PpYZjEP26zVKjMwBNHpMtJjObqUy8yUZUmgf6pYuf4Q=; b=Mk3jX55P9k5N3wrpiUMx/+6F+cSRag8gV0mvxvBJY5XuqCGmp18hwz9I+/vQLO2vAw 8Zr0jQeKeUbbZkXxozxAvkXY+PO+l0n8TJc12W/wtGG3UV1V6lHRIjmyDHGA+SKI9F/P LEz/L7jmBN59j580txpkr42HZFXU5QeOkiAGORYA4l3w+uethVJjV+ex/gWNLS+O29tL ZjjOX3AwPtRlU/53kRpovVmIjM81ntzHzvPvZWSFJ5IGrpMANh/SouZHW3AjhWGDaw5g 0tcqNSTv8UpzQfmbJ5PYFsbwqhU8gw0+wKPYW6g1QyLha2CQaoxMa7nJ8F+HwL3q99+S fvFA== X-Gm-Message-State: AOAM532jcsFOp5OCnt+8f00NG8l06GH2KuCkDsHcySSuR76dZg5+U/2H G7ZZ0p7oj7OZn9qQz5xateDjx9ztYYYiFNT14qTiFKd6 X-Google-Smtp-Source: ABdhPJzaHRJGv41umjZUT6AWRoJ0hg08HJD/Q0QNl91/Xi5EEqcpSyQa+Guj5qVwAqgXdSiHNrzOVGFmTNFOuW5iTTs= X-Received: by 2002:a05:6808:68f:: with SMTP id k15mr6965341oig.5.1638376947834; Wed, 01 Dec 2021 08:42:27 -0800 (PST) MIME-Version: 1.0 References: <010901d7e5c1$4a0c7c20$de257460$@gmail.com> <202111301530.1AUFU2eC015214@freefriends.org> <202111301850.1AUIovEG006894@darkstar.fourwinds.com> <202111302307.1AUN7TBv066715@darkstar.fourwinds.com> <202112010500.1B150a48077541@darkstar.fourwinds.com> <028601d7e67c$87e1bbd0$97a53370$@gmail.com> In-Reply-To: <028601d7e67c$87e1bbd0$97a53370$@gmail.com> From: ron minnich Date: Wed, 1 Dec 2021 08:42:16 -0800 Message-ID: To: TUHS main list Content-Type: text/plain; charset="UTF-8" Subject: Re: [TUHS] Encoding an ISA: Random Logic vs. Control Stores 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: , Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" I used to design hardware in those days, and had a soldering iron and a PDP 11/45 board on the same bench, unsuccessfully, so here goes. It's interesting to consider the PDP-8 and -11, and the progression of hardware. The -11 was way different than the -8: I still have some -8 boards, on which you can see the transistors and such needed to implement state and gates. The -11s had TTL. At the time, a package with four logic elements was a big deal. so the -8 had "a gate per 2x3 inch card" or so. The -11 had about 8x11 boards with, by my count on the 11/20, around 100+ gates (I've got some cards still ...). Again, multiple logic elements in a 14-dip were an amazing step forward. If you look at those boards, you see lots of 14-DIP with quad NAND, AND, NOR, 2 flops per package, and that's about it. In this world, where a gate costs about $1, you think about everything. Look carefully, and you can see the traces were laid out by hand; some of us remember the rooms full of light panels and the red tape you used to lay out the board. Not that I designed CPUs, but having used this gear, lived in the culture, I'd argue that bit layouts of instructions did in fact matter. The TTL MUX parts were yet to appear. The board layout, package design, cost of a wire, instruction format: all to some extent intertwined. You could look at the hardware design and draw a connection right back to instruction coding. It was all of a piece. The luxury of a ROM or MUX that picked instructions apart for you? Not at that time. As for random logic ... the things we did back then. The discipline of design for test, which we take for granted today as JTAG, was some time in the future. And some of you no doubt remember the unibus ... and the practice of "margining the bus." I.e., slow it the hell down so maybe it would not get data errors. Or maybe, even, "let's put a cap here to add some delay constant" -- people really did that stuff. It's amazing anything worked. But when a gate costs a buck, you do what you do. On Tue, Nov 30, 2021 at 10:30 PM wrote: > > Said Jon: > > " In a microcoded machine, the same hardware is used for every > microinstruction. In random logic, custom designed circuitry is used for > each special case." > > Best way to get a handle on the distinction is to read up on the originator > of the concept, Maurice Wilkes: > > https://en.wikipedia.org/wiki/Maurice_Wilkes > https://amturing.acm.org/info/wilkes_1001395.cfm > > The original paper: > > http://www.cs.princeton.edu/courses/archive/fall09/cos375/BestWay.pdf > > "The Best Way to Design an Automatic Calculating Machine" (1951) > > ----- >