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 25004 invoked from network); 21 Apr 2023 14:37:38 -0000 Received: from minnie.tuhs.org (2600:3c01:e000:146::1) by inbox.vuxu.org with ESMTPUTF8; 21 Apr 2023 14:37:38 -0000 Received: from minnie.tuhs.org (localhost [IPv6:::1]) by minnie.tuhs.org (Postfix) with ESMTP id E36F440A74; Sat, 22 Apr 2023 00:37:31 +1000 (AEST) Received: from mercury.lcs.mit.edu (mercury.lcs.mit.edu [18.26.0.122]) by minnie.tuhs.org (Postfix) with ESMTPS id 2255240A6D for ; Sat, 22 Apr 2023 00:37:15 +1000 (AEST) Received: by mercury.lcs.mit.edu (Postfix, from userid 11178) id 492DF18C0A3; Fri, 21 Apr 2023 10:37:13 -0400 (EDT) To: tuhs@tuhs.org Message-Id: <20230421143713.492DF18C0A3@mercury.lcs.mit.edu> Date: Fri, 21 Apr 2023 10:37:13 -0400 (EDT) From: jnc@mercury.lcs.mit.edu (Noel Chiappa) Message-ID-Hash: SEBU3ERFSVEEYEGP4KLQAUDKQA25YUQ3 X-Message-ID-Hash: SEBU3ERFSVEEYEGP4KLQAUDKQA25YUQ3 X-MailFrom: jnc@mercury.lcs.mit.edu X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: jnc@mercury.lcs.mit.edu X-Mailman-Version: 3.3.6b1 Precedence: list Subject: [TUHS] Re: UNIX "Machine Layer" Standards List-Id: The Unix Heritage Society mailing list Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: > From: Paul Ruizendaal > something like a boot rom only became the norm in the late > 70's. Before that, one keyed in two dozen words with a tiny program to > load the first boot stage. A little wrong on that date. Even the PDP-11/20 (the first -11) had a boot ROM: https://gunkies.org/wiki/BM792_ROM which appreared in mid-1971 (about a year after the release of the /20). DEC sold them pre-programmed, but one could 'program' one onself, if one wanted - with a soldering iron! (Check out the image! I actually did that to one that I was given, that had been eviscerated by someone.) From then on (follow the category link), the rest used PROM chips. > From: Warner Losh > Oftentimes, the interrupt vector was in the lowest core addresses It's worth remembering that in the early period, that restriction to low addresses was built into the hardware (in an amusing way :-). Take the DL11: https://gunkies.org/wiki/DL11_asynchronous_serial_line_interface which was sort of mandatory as the 'console' serial interface on most early -11's (until the DL11-W appeared; more on its big improvement in a second). It set the interrupt vector with _jumpers_. (You want to change the interrupt vector? Dig out your soldering iron! :-) There were only 6 jumpers - one each for address bits 3 through 8. So the largest vector you could set was 0770. The DL11-W was a big step forward - it replaced the jumpers with a DIP switch! :-) Still only six bits, though. :-) Noel