[TUHS] pseudo tty history

[TUHS] pseudo tty history

[ron minnich]

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so the question of pseudo tty came up today.

My memory is that it started with TOPS-10, though I doubt I know enough.
Vague memory says there was a PTY: device.

Further, I believe pty came in from UCB ca 1977 or so?

I'm wondering if people who were Present at the Creation can fill in the
gaps.

Thanks

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[TUHS] Re: pseudo tty history

[Bakul Shah via TUHS]

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From https://en.wikipedia.org/wiki/Pseudoterminal

Pseudoterminals were present in the DEC <https://en.wikipedia.org/wiki/Digital_Equipment_Corporation> PDP-6 <https://en.wikipedia.org/wiki/PDP-6> Timesharing Monitor at least as early as 1967, and were used to implement batch processing. They are described in the documentation for the succeeding TOPS-10 <https://en.wikipedia.org/wiki/TOPS-10> on the PDP-10 <https://en.wikipedia.org/wiki/PDP-10>.[6] <https://en.wikipedia.org/wiki/Pseudoterminal#cite_note-6> Other DEC operating systems also had PTYs, including RSTS/E <https://en.wikipedia.org/wiki/RSTS/E> for the PDP-11 <https://en.wikipedia.org/wiki/PDP-11>, as did the third-party TENEX <https://en.wikipedia.org/wiki/TENEX_(operating_system)> operating system for the PDP-10.

Implementations of Unix pseudo terminals date back to the modifications that RAND and BBN made to a 6th Edition in the late 1970s to support remote access over a network.[7] <https://en.wikipedia.org/wiki/Pseudoterminal#cite_note-7> Modern Unix pseudoterminals originated in 1983 during the development of Eighth Edition Unix <https://en.wikipedia.org/wiki/Version_8_Unix> and were based on a similar feature in TENEX.[8] <https://en.wikipedia.org/wiki/Pseudoterminal#cite_note-8> They were part of the 4.3BSD-Reno <https://en.wikipedia.org/wiki/4.3BSD-Reno>, with a rather cumbersome openpty() interface defined for use.[9] <https://en.wikipedia.org/wiki/Pseudoterminal#cite_note-9>

[In absence of a more authoritative source]

> On Aug 15, 2025, at 3:28 PM, ron minnich <rminnich@gmail.com> wrote:
> 
> so the question of pseudo tty came up today. 
> 
> My memory is that it started with TOPS-10, though I doubt I know enough. Vague memory says there was a PTY: device.
> 
> Further, I believe pty came in from UCB ca 1977 or so? 
> 
> I'm wondering if people who were Present at the Creation can fill in the gaps.
> 
> Thanks


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[TUHS] Re: pseudo tty history

[Ron Natalie]

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I think that wikipedia history is somewhat garbled when it comes to the 
UNIX implementations.


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[TUHS] Re: pseudo tty history

[ron minnich]

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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@ronnatalie.com> wrote:

> I think that wikipedia history is somewhat garbled when it comes to the
> UNIX implementations.
>
>
>

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[TUHS] Re: pseudo tty history

[Warner Losh]

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At the very least, 4.2BSD had them for telnet and rlogin. They were static,
though. You had to MAKEDEV enough units.

Warner

On Fri, Aug 15, 2025, 5:00 PM ron minnich <rminnich@gmail.com> wrote:

> 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@ronnatalie.com> wrote:
>
>> I think that wikipedia history is somewhat garbled when it comes to the
>> UNIX implementations.
>>
>>
>>

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[TUHS] Re: pseudo tty history

[Tom Lyon]

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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@bsdimp.com> wrote:

> At the very least, 4.2BSD had them for telnet and rlogin. They were
> static, though. You had to MAKEDEV enough units.
>
> Warner
>
> On Fri, Aug 15, 2025, 5:00 PM ron minnich <rminnich@gmail.com> wrote:
>
>> 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@ronnatalie.com> wrote:
>>
>>> I think that wikipedia history is somewhat garbled when it comes to the
>>> UNIX implementations.
>>>
>>>
>>>

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[TUHS] Re: pseudo tty history

[Jonathan Gray]

On Fri, Aug 15, 2025 at 04:19:38PM -0700, Tom Lyon 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??

Rich Morin scanned CSRG TR 3 & 4
https://www.tuhs.org/pipermail/tuhs/2020-January/020006.html
https://www.tuhs.org/pipermail/tuhs/2020-January/020033.html

The versions I have are from there, but the cfcl.com links no longer work.
Warren uploaded them to the Internet Archive:

CSRG TR 3
William Joy, Robert Fabry
An Architecture for Interprocess Communication in UNIX
DRAFT of June 22, 1981
https://archive.org/details/csrgtr3

CSRG TR 4
William Joy, Robert Fabry
Proposals for enhancement of UNIX on the VAX
July 21, 1981, Revised August 31, 1981
https://archive.org/details/csrgtr4

[TUHS] Re: pseudo tty history

[Jeremy C. Reed]

"In January 1981, Toy worked on adding the pseudo-teletype (ptty) 
drivers that were overhauled and ported to VMUNIX by Borden in July 
1980. (This ptty code came from Borden's earlier Harvard work.)"

(Borden told me it came from his Harvard work.)

SCCS also shows

../archives/1980s/4.1c.1/sys/sys/SCCS/s.tty_pty.c- * Overhauled, and 
ported to VAX/VMUNIX (V7) Bruce Borden, July 80

../archives/1980s/4.1c.1/sys/sys/SCCS/s.tty_pty.c: * Modified and 
integrated into 4bsd by Kipp Hickman and Michael Toy

Several commits around there for toy


echo Fbzrqnl V jvyy svavfu zl obbx. | \
  tr "VFnoqrsuvxyzabfjl" "ISabdefhiklmnoswy"

[TUHS] Re: pseudo tty history

[ron minnich]

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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@gmail.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@bsdimp.com> wrote:
>
>> At the very least, 4.2BSD had them for telnet and rlogin. They were
>> static, though. You had to MAKEDEV enough units.
>>
>> Warner
>>
>> On Fri, Aug 15, 2025, 5:00 PM ron minnich <rminnich@gmail.com> wrote:
>>
>>> 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@ronnatalie.com> wrote:
>>>
>>>> I think that wikipedia history is somewhat garbled when it comes to the
>>>> UNIX implementations.
>>>>
>>>>
>>>>

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[TUHS] Re: pseudo tty history

[Ron Natalie]

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We had virtual links that just used clever use of pipes around the 
shell.  It was clunky.   Even in the NTP (pre-internet Arpanet) days we 
had ptys.



------ Original Message ------
From "ron minnich" <rminnich@gmail.com>
To "Tom Lyon" <pugs78@gmail.com>
Cc "Bakul Shah" <bakul@iitbombay.org>; "The Eunuchs Hysterical Society" 
<tuhs@tuhs.org>
Date 8/15/2025 9:49:16 PM
Subject [TUHS] Re: pseudo tty history

>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@gmail.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@bsdimp.com> wrote:
>>>At the very least, 4.2BSD had them for telnet and rlogin. They were 
>>>static, though. You had to MAKEDEV enough units.
>>>
>>>Warner
>>>
>>>On Fri, Aug 15, 2025, 5:00 PM ron minnich <rminnich@gmail.com> wrote:
>>>>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@ronnatalie.com> 
>>>>wrote:
>>>>>I think that wikipedia history is somewhat garbled when it comes to 
>>>>>the UNIX implementations.
>>>>>
>>>>>

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[TUHS] Re: pseudo tty history

[Clem Cole]

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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@ronnatalie.com> wrote:

> I think that wikipedia history is somewhat garbled when it comes to the
> UNIX implementations.
>
>
>

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[TUHS] Re: pseudo tty history

[Clem Cole]

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That version came from the BBN code.

On Fri, Aug 15, 2025 at 4:19 PM Tom Lyon <pugs78@gmail.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@bsdimp.com> wrote:
>
>> At the very least, 4.2BSD had them for telnet and rlogin. They were
>> static, though. You had to MAKEDEV enough units.
>>
>> Warner
>>
>> On Fri, Aug 15, 2025, 5:00 PM ron minnich <rminnich@gmail.com> wrote:
>>
>>> 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@ronnatalie.com> wrote:
>>>
>>>> I think that wikipedia history is somewhat garbled when it comes to the
>>>> UNIX implementations.
>>>>
>>>>
>>>>

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[TUHS] Re: pseudo tty history

[Bakul Shah via TUHS]

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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.


> On Aug 15, 2025, at 6:49 PM, ron minnich <rminnich@gmail.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@gmail.com <mailto:pugs78@gmail.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@bsdimp.com <mailto:imp@bsdimp.com>> wrote:
>>> At the very least, 4.2BSD had them for telnet and rlogin. They were static, though. You had to MAKEDEV enough units.
>>> 
>>> Warner
>>> 
>>> On Fri, Aug 15, 2025, 5:00 PM ron minnich <rminnich@gmail.com <mailto:rminnich@gmail.com>> wrote:
>>>> 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@ronnatalie.com <mailto:ron@ronnatalie.com>> wrote:
>>>>> I think that wikipedia history is somewhat garbled when it comes to the UNIX implementations.   
>>>>> 
>>>>> 


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[TUHS] Re: pseudo tty history

[Clem Cole]

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Watch the dates - that's not UNIX.  In 1973, Version 4 Unix is first
released outside of BTL, so the Harvard system being talked about in RFC 89
is probably an 18 bit ??PDP6 maybe??.

On Fri, Aug 15, 2025 at 8:24 PM Bakul Shah via TUHS <tuhs@tuhs.org> 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.
>
>
> On Aug 15, 2025, at 6:49 PM, ron minnich <rminnich@gmail.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@gmail.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@bsdimp.com> wrote:
>>
>>> At the very least, 4.2BSD had them for telnet and rlogin. They were
>>> static, though. You had to MAKEDEV enough units.
>>>
>>> Warner
>>>
>>> On Fri, Aug 15, 2025, 5:00 PM ron minnich <rminnich@gmail.com> wrote:
>>>
>>>> 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@ronnatalie.com> wrote:
>>>>
>>>>> I think that wikipedia history is somewhat garbled when it comes to
>>>>> the UNIX implementations.
>>>>>
>>>>>
>>>>>
>

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[TUHS] Re: pseudo tty history

[Aron Insinga]

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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:
> Watch the dates - that's not UNIX.  In 1973, Version 4 Unix is first 
> released outside of BTL, so the Harvard system being talked about in 
> RFC 89 is probably an 18 bit ??PDP6 maybe??.
>
> On Fri, Aug 15, 2025 at 8:24 PM Bakul Shah via TUHS <tuhs@tuhs.org> 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.
>
>
>>     On Aug 15, 2025, at 6:49 PM, ron minnich <rminnich@gmail.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@gmail.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@bsdimp.com>
>>         wrote:
>>
>>             At the very least, 4.2BSD had them for telnet and rlogin.
>>             They were static, though. You had to MAKEDEV enough units.
>>
>>             Warner
>>
>>             On Fri, Aug 15, 2025, 5:00 PM ron minnich
>>             <rminnich@gmail.com> wrote:
>>
>>                 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@ronnatalie.com> wrote:
>>
>>                     I think that wikipedia history is somewhat
>>                     garbled when it comes to the UNIX implementations.
>>
>>
>

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[TUHS] Re: pseudo tty history

[Clem Cole]

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Right.  What I do not know is what early machines Harvard had from DEC.
MIT had the 18 and 36 bit series which was what I was implying.  The key
point though is that if Harvard was the root of the PTY tree it would have
been on one of those systems not a Unix system because Unix did not come to
Harvard until 1974 and RFC 89 was 1971 and RFC 46 in 1970

Sent from a handheld expect more typos than usual


On Fri, Aug 15, 2025 at 8:50 PM Aron Insinga <aki@insinga.com> wrote:

> 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:
>
> Watch the dates - that's not UNIX.  In 1973, Version 4 Unix is first
> released outside of BTL, so the Harvard system being talked about in RFC 89
> is probably an 18 bit ??PDP6 maybe??.
>
> On Fri, Aug 15, 2025 at 8:24 PM Bakul Shah via TUHS <tuhs@tuhs.org> 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.
>>
>>
>> On Aug 15, 2025, at 6:49 PM, ron minnich <rminnich@gmail.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@gmail.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@bsdimp.com> wrote:
>>>
>>>> At the very least, 4.2BSD had them for telnet and rlogin. They were
>>>> static, though. You had to MAKEDEV enough units.
>>>>
>>>> Warner
>>>>
>>>> On Fri, Aug 15, 2025, 5:00 PM ron minnich <rminnich@gmail.com> wrote:
>>>>
>>>>> 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@ronnatalie.com>
>>>>> wrote:
>>>>>
>>>>>> I think that wikipedia history is somewhat garbled when it comes to
>>>>>> the UNIX implementations.
>>>>>>
>>>>>>
>>>>>>
>>
>

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[TUHS] Re: pseudo tty history

[Aron Insinga]

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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
> Sites known to have PDP-1's based on DECUS submissions:
> ...
> Harvard University                     Dec 64
> ...
> MIT Lincoln Laboratory Group 22        May 65
> MIT Laboratory For Nuclear Science     Apr 65
> MIT Project MAC                        Jul 64
> MIT RLE                                Sep 65

By serial number:
> 05  PDP-1C  MIT (RLE)
> 26  PDP-1C  MIT
> 37  PDP-1C  MIT Lincoln Labs                11/65
> 40  PDP-1C  MIT (MAC)                        64(?)
> 41  PDP-1C  Harvard
> 53  PDP-1   MIT

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:
> Right.  What I do not know is what early machines Harvard had from 
> DEC.  MIT had the 18 and 36 bit series which was what I was implying.  
> The key point though is that if Harvard was the root of the PTY tree 
> it would have been on one of those systems not a Unix system because 
> Unix did not come to Harvard until 1974 and RFC 89 was 1971 and RFC 46 
> in 1970
>
> Sent from a handheld expect more typos than usual
>
>
> On Fri, Aug 15, 2025 at 8:50 PM Aron Insinga <aki@insinga.com> wrote:
>
>     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:
>>     Watch the dates - that's not UNIX.  In 1973, Version 4 Unix is
>>     first released outside of BTL, so the Harvard system being talked
>>     about in RFC 89 is probably an 18 bit ??PDP6 maybe??.
>>
>>     On Fri, Aug 15, 2025 at 8:24 PM Bakul Shah via TUHS
>>     <tuhs@tuhs.org> 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.
>>
>>
>>>         On Aug 15, 2025, at 6:49 PM, ron minnich
>>>         <rminnich@gmail.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@gmail.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@bsdimp.com> wrote:
>>>
>>>                 At the very least, 4.2BSD had them for telnet and
>>>                 rlogin. They were static, though. You had to MAKEDEV
>>>                 enough units.
>>>
>>>                 Warner
>>>
>>>                 On Fri, Aug 15, 2025, 5:00 PM ron minnich
>>>                 <rminnich@gmail.com> wrote:
>>>
>>>                     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@ronnatalie.com> wrote:
>>>
>>>                         I think that wikipedia history is somewhat
>>>                         garbled when it comes to the UNIX
>>>                         implementations.
>>>
>>>
>>
>

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[TUHS] Re: pseudo tty history

[Larry McVoy]

On Sat, Aug 16, 2025 at 08:21:30PM -0400, Aron Insinga wrote:
> 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."

Wasn't there a PDP-<something> at MIT, I think, that had a switch labeled
"magic" and "more magic" that had wires that went nowhere but it only 
worked when set to "more magic"?  I'm sure I have the details wrong but
I have a pretty strong memory of that.  Anyone able to confirm?

[TUHS] Re: pseudo tty history

[Al Kossow]

On 8/16/25 6:05 PM, Larry McVoy wrote:
> On Sat, Aug 16, 2025 at 08:21:30PM -0400, Aron Insinga wrote:
>> 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."
> 
> Wasn't there a PDP-<something> at MIT, I think, that had a switch labeled
> "magic" and "more magic" that had wires that went nowhere but it only
> worked when set to "more magic"?  I'm sure I have the details wrong but
> I have a pretty strong memory of that.  Anyone able to confirm?
> 

https://github.com/PDP-10/its/issues/1232

the switch still exists

[TUHS] Re: pseudo tty history

[Al Kossow]

On 8/16/25 6:13 PM, Al Kossow wrote:
> On 8/16/25 6:05 PM, Larry McVoy wrote:
>> On Sat, Aug 16, 2025 at 08:21:30PM -0400, Aron Insinga wrote:
>>> 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."
>>
>> Wasn't there a PDP-<something> at MIT, I think, that had a switch labeled
>> "magic" and "more magic" that had wires that went nowhere but it only
>> worked when set to "more magic"?  I'm sure I have the details wrong but
>> I have a pretty strong memory of that.  Anyone able to confirm?
>>
> 
> https://github.com/PDP-10/its/issues/1232
> 
> the switch still exists
> 
https://www.youtube.com/watch?v=_y0nVBpclIE

[TUHS] Re: pseudo tty history

[Lawrence Stewart]

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”.

> On Aug 16, 2025, at 21:05, Larry McVoy <lm@mcvoy.com> wrote:
> 
> On Sat, Aug 16, 2025 at 08:21:30PM -0400, Aron Insinga wrote:
>> 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."
> 
> Wasn't there a PDP-<something> at MIT, I think, that had a switch labeled
> "magic" and "more magic" that had wires that went nowhere but it only 
> worked when set to "more magic"?  I'm sure I have the details wrong but
> I have a pretty strong memory of that.  Anyone able to confirm?

[TUHS] Re: pseudo tty history

[Al Kossow]

On 8/16/25 6:16 PM, Al Kossow wrote:
> On 8/16/25 6:13 PM, Al Kossow wrote:
>> On 8/16/25 6:05 PM, Larry McVoy wrote:
>>> On Sat, Aug 16, 2025 at 08:21:30PM -0400, Aron Insinga wrote:
>>>> 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."
>>>
>>> Wasn't there a PDP-<something> at MIT, I think, that had a switch labeled
>>> "magic" and "more magic" that had wires that went nowhere but it only
>>> worked when set to "more magic"?  I'm sure I have the details wrong but
>>> I have a pretty strong memory of that.  Anyone able to confirm?
>>>
>>
>> https://github.com/PDP-10/its/issues/1232
>>
>> the switch still exists
>>
> https://www.youtube.com/watch?v=_y0nVBpclIE
> 

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

[TUHS] Re: magic, was pseudo tty history

[John Levine]

It appears that Larry McVoy <lm@mcvoy.com> said:
>On Sat, Aug 16, 2025 at 08:21:30PM -0400, Aron Insinga wrote:
>> 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."

PDP-6's were flaky even when they were new, due to large circuit cards
with unreliable connectors.  I gather a standard diagnostic technique
was to tap all the cards with a rubber mallet to reseat them.  The KA-10
used much smaller and more reliable Flip Chip cards.

>Wasn't there a PDP-<something> at MIT, I think, that had a switch labeled
>"magic" and "more magic" that had wires that went nowhere but it only 
>worked when set to "more magic"?  I'm sure I have the details wrong but
>I have a pretty strong memory of that.  Anyone able to confirm?

Probably this one:

https://boingboing.net/2022/08/11/a-story-about-a-weird-magic-switch-at-mit.html

[TUHS] Re: pseudo tty history

[Larry McVoy]

On Sat, Aug 16, 2025 at 06:13:33PM -0700, Al Kossow wrote:
> On 8/16/25 6:05 PM, Larry McVoy wrote:
> >On Sat, Aug 16, 2025 at 08:21:30PM -0400, Aron Insinga wrote:
> >>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."
> >
> >Wasn't there a PDP-<something> at MIT, I think, that had a switch labeled
> >"magic" and "more magic" that had wires that went nowhere but it only
> >worked when set to "more magic"?  I'm sure I have the details wrong but
> >I have a pretty strong memory of that.  Anyone able to confirm?
> >
> 
> https://github.com/PDP-10/its/issues/1232
> 
> the switch still exists

Nice to know I didn't make all that story up in my boomer brain.  That story
is exactly as I remember it except for this

    I still have that switch in my basement. Maybe I'm silly, but I
    usually keep it set on "more magic".

I hadn't heard that part.

Thanks for the memories, it's part of the history.

--lm

[TUHS] Re: magic, was pseudo tty history

[Aron Insinga]

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-from-the-mainframe-to-the-minicomputer-part-3-dec-and-data-general/)

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:
> It appears that Larry McVoy <lm@mcvoy.com> said:
>> On Sat, Aug 16, 2025 at 08:21:30PM -0400, Aron Insinga wrote:
>>> 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."
> PDP-6's were flaky even when they were new, due to large circuit cards
> with unreliable connectors.  I gather a standard diagnostic technique
> was to tap all the cards with a rubber mallet to reseat them.  The KA-10
> used much smaller and more reliable Flip Chip cards.
>
>> Wasn't there a PDP-<something> at MIT, I think, that had a switch labeled
>> "magic" and "more magic" that had wires that went nowhere but it only
>> worked when set to "more magic"?  I'm sure I have the details wrong but
>> I have a pretty strong memory of that.  Anyone able to confirm?
> Probably this one:
>
> https://boingboing.net/2022/08/11/a-story-about-a-weird-magic-switch-at-mit.html