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 16918 invoked from network); 1 Dec 2021 05:02:06 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 1 Dec 2021 05:02:06 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 9492C9CF27; Wed, 1 Dec 2021 15:01:57 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 9C5C79C78B; Wed, 1 Dec 2021 15:00:41 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id 656949C78B; Wed, 1 Dec 2021 15:00:38 +1000 (AEST) Received: from darkstar.fourwinds.com (fourwinds.com [63.64.179.162]) by minnie.tuhs.org (Postfix) with ESMTPS id F0A2994502 for ; Wed, 1 Dec 2021 15:00:37 +1000 (AEST) Received: from darkstar.fourwinds.com (localhost [127.0.0.1]) by darkstar.fourwinds.com (8.16.1/8.15.2) with ESMTP id 1B150bfY077544 for ; Tue, 30 Nov 2021 21:00:37 -0800 Received: from darkstar.fourwinds.com (jon@localhost) by darkstar.fourwinds.com (8.16.1/8.15.2/Submit) with ESMTP id 1B150a48077541 for ; Tue, 30 Nov 2021 21:00:37 -0800 Message-Id: <202112010500.1B150a48077541@darkstar.fourwinds.com> From: Jon Steinhart To: TUHS main list In-reply-to: References: <010901d7e5c1$4a0c7c20$de257460$@gmail.com> <202111301530.1AUFU2eC015214@freefriends.org> <202111301850.1AUIovEG006894@darkstar.fourwinds.com> <202111302307.1AUN7TBv066715@darkstar.fourwinds.com> Comments: In-reply-to Henry Bent message dated "Tue, 30 Nov 2021 18:18:43 -0500." MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <77539.1638334836.1@darkstar.fourwinds.com> Date: Tue, 30 Nov 2021 21:00:36 -0800 X-JON-SPAM: local delivery 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" Henry Bent writes: > On Tue, 30 Nov 2021 at 18:10, Jon Steinhart wrote: > > > Humm writes: > > > Quoth Jon Steinhart: > > > >arnold@skeeve.com writes: > > > >> Can someone please explain why it's called "random" logic? Discrete > > > >> logic I understand (more or less), but I've not heard the term > > "random" > > > >> used in this context before now. > > > > > > > >Well, as a recovered random logic designer, I think that the name comes > > > >from there being no particular structure to the logic. Many parts of > > > >logic design are very regular, think memory. But that regularity doesn't > > > >exist when, for example, decoding irregular instructions. > > > > > > Now that's a "random" definition. > > > > > > -- > > > Humm > > > > OK, I'll try again. For anybody familiar with Portland, Oregon, it's the > > difference between driving in Northwest where there's a rectangular grid > > numbered in one direction and alphabetical in the other, and approaching > > the Ross Island Bridge from the west side which appears to be designed by > > someone following a goat while tripping their brains out. One can address > > Northwest Portland quite easily unlike getting onto the Ross Island Bridge. > > > > So - and as I say this as someone who has no direct experience with this > level of logic - everything is directly addressable but the difference is > in how you get there? Sorry my analogy didn't work. Look at a photomicrograph of a chip; at least to me it's pretty obvious where the random logic is located. Here's another try. In a microcoded machine, the same hardware is used for every microinstruction. In random logic, custom designed circuitry is used for each special case.