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, RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 25114 invoked from network); 9 Dec 2020 19:26:46 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 9 Dec 2020 19:26:46 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 7C49A944FC; Thu, 10 Dec 2020 05:26:38 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 42D4093D29; Thu, 10 Dec 2020 05:25:42 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id 9FB8C93D29; Thu, 10 Dec 2020 05:25:38 +1000 (AEST) Received: from mercury.lcs.mit.edu (mercury.lcs.mit.edu [18.26.0.122]) by minnie.tuhs.org (Postfix) with ESMTPS id EC40793D28 for ; Thu, 10 Dec 2020 05:25:37 +1000 (AEST) Received: by mercury.lcs.mit.edu (Postfix, from userid 11178) id 9A55018C088; Wed, 9 Dec 2020 14:25:36 -0500 (EST) To: tuhs@tuhs.org Message-Id: <20201209192536.9A55018C088@mercury.lcs.mit.edu> Date: Wed, 9 Dec 2020 14:25:36 -0500 (EST) From: jnc@mercury.lcs.mit.edu (Noel Chiappa) Subject: Re: [TUHS] Were cron and at done at the same time? Or one before the other? 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: jnc@mercury.lcs.mit.edu Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" > From: Niklas Karlsson > Just consider Multics, or IBM's "Future System". Here's a nice irony for you: one of the key people in killing off FS was reported to me (by someone who should have known) to be Jerry Saltzer (of Multics fame). That wasn't the only time he did something like thst, either; when MIT leaned on him to take over Athena, the first thing he did was to take a lot of their ambitious system plans, and ditch them; they fell back to mostly 'off the shelf' stuff: pretty much vanilla 4.2, etc. Multics itself has an interesting story, quite different from the popular image among those who know little (or nothing) of it. The system, as it was when Honeywell pulled the plug on further generations of new hardware (in the mid-80's) was very different from the system as originally envisaged by MIT (in the mid-60's); it had undergone a massive amount 'experience-based evolution' during those 20 years. For instance, the original concept was to have a process per command (like Unix), but that was dropped early on (because Multics processes were too 'expensive'); they wound up going with doing commands with inter-segment procedure calls. (Which has the nice benefit that when a command faults, you can get dropped right into the debugger, with the failed instance there to look at.) If you read the Organick book on Multics, it describes a much different system: e.g. in Organick there's a 'linkage segment' (used for inter-segment pointers, in pure-code segments) per code segment, but in reality Multics, as distributed, used a single 'combined linkage segment' (which also contained the stack, also unlike the original design, where the stack was a separate segment). There were also numerous places where major sub-systems were re-implemeneted from scratch, with major changes (often great simplifications): one major re-do was the New Storage System, but that one had major new features (based on operationally-shown needs, like the 4.1/.2 Fast File System), so it's not a 'simplification' case. There's one I read about which was much simpler the second time it was implemented, I think it was IPC? Noel