That was my guess. I figured the people who did the work are on this list, and primary sources rule. On Fri, Aug 15, 2025 at 3:56 PM Ron Natalie <ron(a)ronnatalie.com> wrote:

Yeah, I was thinking that 4.1c BSD must've had them for rlogin and telnet. Which got me looking for Fabry and Bill Joy's design/planning documents for 4.2, which are not in the TUHS archives. Anyone got them?? On Fri, Aug 15, 2025 at 4:15 PM Warner Losh <imp(a)bsdimp.com> wrote:

was there ever a telnet or other remote access program that predated ptys on Unix? Was telnet the driving force for ptys? Did the folks implementing Unix networking bring in ptys before, or as part of, or after networking, i.e. did folks building networking for Unix realize they needed ptys once they started working on telnet, or did they plan for ptys from the get go? I was an observer for some of this stuff, but as a 20-year-old at UDEL I was also quite out of the loop. I also realize there were multiple Unix networking efforts, so this question is somewhat simplistic. I'm assuming rsh came a bit later. On Fri, Aug 15, 2025 at 4:19 PM Tom Lyon <pugs78(a)gmail.com> wrote:

From RFC 89 (dated 19 January 1971) titled "Some historic moments in networking": Second, the Harvard system has temporarily implemented this remote network console interface feature using a DEC style pseudo-teletype (PTY). From RFC 46 (dated April 1970) titled "'ARPA Network Protocol Notes": 3. A standard way for a newly created process to initiate pseudo- typewriter communication with the foreign process which requested its creation.

The https://datatracker.ietf.org/doc/html/rfc89 mentions a PDP-6 and PDP-10s which are 36-bit twos complement machines, and a DEC PDP-1 which was an 18-bit one's complement  machine.  The "graphics-oriented" PDP-1 probably had the well-known Type 30 display which used a large round radar-type CRT thanks to the Project SAGE tradition, but there were a couple of other graphics display options for the PDP-1. https://www.computerhistory.org/pdp-1/graphics/ - Aron On 8/15/25 23:35, Clem Cole wrote:

The RFC refers to "the Harvard PDP-10 System" and "Harvard's PDP-1" in the first paragraph, and the "MITDG PDP-6/10" (so that's 2 machines but eventually MIT had a gaggle of PDP-10s) in the second paragraph.  And  of course MIT had a PDP-1, where Spacewar was developed and first played.  I don't know the arrival/exit dates of the machines. Here are some dates, but I don't know if they are just samples based on the earliest DECUS submission from there, or installation dates. The Harvard museum (which has pieces of the Mark I) may know more about when different machines were installed and removed. http://www.bitsavers.org/pdf/dec/pdp1/PDP-1_SerialNumbers.txt By serial number: Side note: I saw the MIT PDP-6 with its chess trophies on top of it during the Blizzard of '78.  (After I interviewed at DEC, I made my way from Marlborough through the rapidly-intensifying snow to Cambridge to visit someone from High School.  I ended up crashing on a dorm sofa from the day the blizzard hit until the airport in Boston reopened which was about a week.)  The PDP-6 had a sign on it that said something like "This machine is old and flaky so don't touch it unless you know what you are doing." - Aron On 8/16/25 10:57, Clem Cole wrote:

On 8/16/25 6:05 PM, Larry McVoy wrote: https://github.com/PDP-10/its/issues/1232 the switch still exists

On 8/16/25 6:16 PM, Al Kossow wrote: wow, that description is completely wrong. the PDP-6 was built from discrete PNP negative logic, not TTL, at which point I stopped listening it was useful for the picture of the switch though

My favorite MIT 10 switch was something like “Split Sync Inhibit Enable Override” Never saw it myself. It had something to do with atomic instructions that required “split sync”.

Yes, the problem with the large boards made DEC stick with the small Flip-Chip cards for many years.  (Single height, single width Flip-Chips are about the same size as IBM SMS cards; they both used the same wire-wrap backplane and they both used the card edge to form an integral connector.  At least for the PDP-8 they got to use some double height single width boards for things like the AC and registers bit slices.) (FWIW, I am curious about how that Sylvania backplane came about.  A Sylvania idea?  IBM?  Gardner-Denver?) The problems with the PDP-6 and its large boards were one reason DEC co-founder Harlan Anderson left. (https://videogamehistorian.wordpress.com/2014/12/11/historical-interlude-fr…) The PDP-11 and KL10 projects finally got around the fear of large boards at DEC.  (IIUC, the very large boards in the Data General Nova were one reason for its low cost; I wonder if that helped too.)  Maybe because they had 7400 TTL & Motorola ECL (respectively) ICs on the boards instead of discrete transistors. https://bitsavers.trailing-edge.com/pdf/dec/pdp6/F-67_circuitInstr_May66.pdf These important bit-slice modules described on pp 32-33 of that manual: * 6205 AR, MQ, MB, and MI flip-flops.  These were 36-bit registers. It is mentioned that it is 3x the area of DEC's then-standard modules (each of which had 1 22-pin connector) and to provide enough connections, it had 4 22-pin connectors, two on each end, side-by-side.  Gordon Bell once described this module as "Bell's Folly. * 6206 MA, PC, and IR flip-flops.  These were 18-bit (memory address) registers.  It is mentioned that it is 2x the area of DEC's then-standard modules and to provide enough connections, it had 2 of the 22-pin connectors, one on each end.    (I don't know if this was also a significant problem source, or if that was only the 6205.) The problems with these modules was that one end could plug into the backplane, but a bus cable had to be run across the back to connect to all of the modules of the same type.  When a module had to be removed, it often resulted in breaking another module or the cable (I forget if it was one, the other, or both). I believe that the effort to construct the large hand-soldered wire-wrap backplane of the PDP-6 encouraged the company to look into the wirewrap backplane for Flip Chips in the classic PDP-8 (and PDP-7).  This was absolutely critical to getting the PDP-8 down to its price point. Dave Gross [RIP] at DEC (a TX-0 and PDP-1 hacker at MIT before he joined DEC) once said that one problem was the PDP-6 design started with germanium transistors but switched to silicon transistors.  (I haven't looked at the module design transistor types in the above-referenced manual to verify this.) So by the time of the PDP-8 and especially the KL10, I think they had a lot more experience with silicon transistors and the transistors themselves were better. So, with virtually the same architecture & instruction set as the PDP-6, the PDP-10 (KA10) was a big winner.  There were a lot of them on the ARPAnet.  It was not the only time that DEC's first product in a space did not do well, but a successor did very, very well. - Aron On 8/16/25 21:56, John Levine wrote:

Boy, that's an understatement. As best I can tell, the Rand UNIX( ??Bruce Borden??) had them first, then they were in the UofI NCP (Steve Holmgren) and migrated to several places like MIT's ChaosNet, long before the BSD implementation. BSD got them from the BBN TCP, which I think came from MIT's flavor. Still, it might have been from any of the other versions that were around at the time - I must have had a couple of different versions in different kernel sources for different V6 kernel hacks in those days, and I did not write any of them. If you look at the old USENIX tapes, you will likely see a couple of versions. Clem On Fri, Aug 15, 2025 at 3:56 PM Ron Natalie <ron(a)ronnatalie.com> wrote: