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 13883 invoked from network); 17 Sep 2021 15:55:07 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 17 Sep 2021 15:55:07 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 8088F9CAD2; Sat, 18 Sep 2021 01:55:04 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 3B3969CAB3; Sat, 18 Sep 2021 01:54:45 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id 4E0199CAB3; Sat, 18 Sep 2021 01:54:42 +1000 (AEST) X-Greylist: delayed 1157 seconds by postgrey-1.36 at minnie.tuhs.org; Sat, 18 Sep 2021 01:54:41 AEST Received: from mercury.lcs.mit.edu (mercury.lcs.mit.edu [18.26.0.122]) by minnie.tuhs.org (Postfix) with ESMTPS id 1A0279CAB2 for ; Sat, 18 Sep 2021 01:54:41 +1000 (AEST) Received: by mercury.lcs.mit.edu (Postfix, from userid 11178) id 96CC618C0A6; Fri, 17 Sep 2021 11:35:23 -0400 (EDT) To: tuhs@minnie.tuhs.org Message-Id: <20210917153523.96CC618C0A6@mercury.lcs.mit.edu> Date: Fri, 17 Sep 2021 11:35:23 -0400 (EDT) From: jnc@mercury.lcs.mit.edu (Noel Chiappa) Subject: Re: [TUHS] Unix for PDP11/20 w/o mmu or paging option 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: Roland Huisman > I have a PDP11/20 and I would love to run an early Unix version on > it. ... But it seems that the earliest versions of Unix do not need the > extra memory. Does anyone have RK05 disk images for these early Unix > versions? Although the _kernel_ source for V1 is available: https://minnie.tuhs.org//cgi-bin/utree.pl?file=V1 most of the rest is missing; only 'init' and 'sh' are available. So one would have to write almost _everything_ else. Some commands are available in PDP-11 assembler in later versions, and might be movable without _too_ much work - but one would have to start with the assembler itself, which is luckily in assembler. If I were trying to run 'UNIX' on an -11/20, I think the only reasonable choice would be MINI-UNIX: https://gunkies.org/wiki/MINI-UNIX It's basically V6 UNIX with all use of the PDP-11 memory management removed. The advantage of going MINI-UNIX is that almost all V6 source (applications, drivers, etc) will run on it 'as is'. It does need ~56KB of main memory. If you don't have that much on the -11/20, LSX (links in the above) would be an option; it's very similar to MINI-UNIX, but is trimmed down some, to allow its use on systems with less main memory. I'm not sure if MINI-UNIX has been run on the -11/20, but it _should_ run there; it runs on the -11/05, and the only differences between the /20 and the /05 are that the /20 does not have the RTT instruction (and I just checked, and MINI-UNIX doesn't use RTT), and SWAB doesn't clear the V condition code bit. (There are other minor differences, such as OP Rn, (Rn)+ are different on the -11/20, but that shouldn't be an issue.) Step 1 would be to get MINI-UNIX running on an -11/20 under a simulator; links in the above to get you there. Noel