The Unix Heritage Society mailing list
 help / color / Atom feed
* [TUHS] updated: loop networks at Bell Labs
@ 2020-06-16 22:41 Paul Ruizendaal
  2020-06-19  1:01 ` Heinz Lycklama
  0 siblings, 1 reply; 2+ messages in thread
From: Paul Ruizendaal @ 2020-06-16 22:41 UTC (permalink / raw)
  To: TUHS main list


[-- Attachment #1: Type: text/plain, Size: 2944 bytes --]

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 <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.


[-- Attachment #2: Type: text/html, Size: 3558 bytes --]

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [TUHS] updated: loop networks at Bell Labs
  2020-06-16 22:41 [TUHS] updated: loop networks at Bell Labs Paul Ruizendaal
@ 2020-06-19  1:01 ` Heinz Lycklama
  0 siblings, 0 replies; 2+ messages in thread
From: Heinz Lycklama @ 2020-06-19  1:01 UTC (permalink / raw)
  To: 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.
>


^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, back to index

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-16 22:41 [TUHS] updated: loop networks at Bell Labs Paul Ruizendaal
2020-06-19  1:01 ` Heinz Lycklama

The Unix Heritage Society mailing list

Archives are clonable: git clone --mirror http://inbox.vuxu.org/tuhs

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://inbox.vuxu.org/vuxu.archive.tuhs


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git