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([2601:601:a000:cb0:d84f:599b:79b7:31ad]) by smtp.gmail.com with ESMTPSA id g65sm3950336pfb.61.2020.06.18.18.01.17 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Jun 2020 18:01:17 -0700 (PDT) To: tuhs@minnie.tuhs.org References: <1F6AD3BF-E7E8-49BD-8993-2539A10F1A89@planet.nl> From: Heinz Lycklama Organization: Open Systems Technology Associates Message-ID: <229637de-55f7-56a7-b5ee-4b0a1578b707@osta.com> Date: Thu, 18 Jun 2020 18:01:16 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <1F6AD3BF-E7E8-49BD-8993-2539A10F1A89@planet.nl> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Subject: Re: [TUHS] updated: loop networks at Bell Labs 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: , Reply-To: heinz@osta.com Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" A later memo in 1978 provides a Figure that shows how the I/O Loop was used to support multiple satellite processors. See here: https://www.tuhs.org/Archive/Documentation/TechReports/Heinz_Tech_Memos/TM-78-3114-2_A_Minicomputer_Satellite_Processor_System_19780322.pdf Heinz On 6/16/2020 3:41 PM, Paul Ruizendaal wrote: > With some further reading and research (and the kind help of Heinz > Lycklama and Jon Steinart) I’ve found that my understanding of early > loop networks at Bell Labs confused several different systems. As far > as I can currently tell there were at least 4 different loop networks > developed around 1970 at Murray Hill. > > 1. The first one is the “Newhall Loop” (paper published in 1969). This > loop used twisted pair cabling, ran at about 3Mhz and used variable > sized messages. It seems to have used some sort of token to coordinate > between hosts. This might have been the network that Ken Thompson > recalled as having been in operation when he arrived at the labs in 1966. > > 2. The second one appears to have been the “Pierce Loop”, as described > in 3 BSTJ papers submitted in 1970/71. This one was coax based, used > T1 compatible frames and was used to connect H516 computers with > various bits of equipment. It seems to have had a very short life > span. Part of my confusion was that the term Pierce Loop also appears > to have been used in a generic sense to denote loop networks with > fixed-sized frames. > > 3. The third one is the “Weller Loop” (paper published in 1971). This > loop used coax cabling, ran at 3.3Mhz and used fixed 35 bit > frames/cells. Each cell carried one address byte and two data bytes. > One participant on the loop was the controller and effectively polled > the other stations. In its 1971 form it appears to have been for the > H516’s only and was referred to as a “Serial I/O bus”. This is what > Jon Steinhart was talking about. > > The Weller loop was later redesigned (memo written in 1973) to > interface with PDP-11’s as well. Heinz Lycklama used this loop in 1974 > to connect several systems running (rump) Unix - see his paper about > peripheral Unix here: > https://www.tuhs.org/Archive/Documentation/TechReports/Heinz_Tech_Memos/TM-75-1352-2_Emulation_of_UNIX_on_Peripheral_Processors_19750109.pdf > > This Serial I/O bus remained in use for several years at least. > > 4. The fourth and best known one is the “Spider Loop” (memo published > in 1974, but operational from 1972). Twisted pair cabling, using T1 > compatible frames. In use until about 1978. Main uses appear to have > been the ‘nfs’ file store and the ‘npr’ remote printing service. > > My conclusion from all that is that in 1974 Unix had access to two > networks, Spider and the Serial I/O bus. For both, first experiments > would have been in 1973. It is hard to be sure which one came first. > If I had to venture a guess today, I’d say that Spider connected to > Unix several months before the Weller loop (even though the 1st > generation Weller loop preceded Spider). Maybe the conclusion is that > both happened more or less in parallel: Weller was also one of the > designers of the Spider hardware. >