From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: tuhs-bounces@minnie.tuhs.org X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.1 Received: from minnie.tuhs.org (minnie.tuhs.org [45.79.103.53]) by inbox.vuxu.org (OpenSMTPD) with ESMTP id 2c44dfe3 for ; Mon, 18 Jun 2018 21:14:09 +0000 (UTC) Received: by minnie.tuhs.org (Postfix, from userid 112) id 3F0BEA19E6; Tue, 19 Jun 2018 07:14:08 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id DDAE4A19D4; Tue, 19 Jun 2018 07:13:39 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id F3FEBA19D4; Tue, 19 Jun 2018 07:13:37 +1000 (AEST) Received: from GW.SoftJAR.SE (gw.softjar.se [213.115.73.154]) by minnie.tuhs.org (Postfix) with ESMTP id 27EFEA19D3 for ; Tue, 19 Jun 2018 07:13:37 +1000 (AEST) Received: from Smurf.BQTnet.SE (178-82-175-247.dynamic.hispeed.ch [178.82.175.247]) by GW.SoftJAR.SE (Postfix) with ESMTPSA id 4C03438FCCA; Mon, 18 Jun 2018 23:13:34 +0200 (CEST) (envelope-from bqt@update.uu.se) To: Noel Chiappa , ron@ronnatalie.com, TUHS main list References: <20180618121738.98BD118C087@mercury.lcs.mit.edu> From: Johnny Billquist Message-ID: Date: Mon, 18 Jun 2018 23:13:32 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180618121738.98BD118C087@mercury.lcs.mit.edu> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [TUHS] core X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.20 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" On 2018-06-18 14:17, Noel Chiappa wrote: > > The "separate" bus for the semiconductor memory is just a second Unibus > > Err, no. :-) There is a second UNIBUS, but... its source is a second port on > the FASTBUS memory, the other port goes straight to the CPU. The other UNIBUS > comes out of the CPU. It _is_ possible to join the two UNIBI together, but > on machines which don't do that, the _only_ path from the CPU to the FASTBUS > memory is via the FASTBUS. Ah. You and Ron are right. I am confused. So there were some previous PDP-11 models who did not have their memory on the Unibus. The 11/45,50,55 accessed memory from the CPU not through the Unibus, but through the fastbus, which was a pure memory bus, as far as I understand. You (obviously) could also have memory on the Unibus, but that would be slower then. Ah, and there is a jumper to tell which addresses are served by the fastbus, and the rest then go to the Unibus. Thanks, I had missed these details before. (To be honest, I have never actually worked on any of those machines.) Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt@softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol