[HECnet] Another TOPS-10 DECnet problem

[Thomas DeBellis]

I think Tops-20 had some code for applications terminals, but I don't 
remember where I saw that.  It has hooks for canonical terminals, but I 
think that may be DEC's adaptation of MIT's SUPDUP code.

May I ask you to clarify what you mean by 'no hard limit'?  Do you mean 
that the configuration parameter is effectively infinite (I.E., a 31 bit 
positive number) or that the system will dynamically allocate jobs and 
tasks as they are requested?

Either way, that is remarkably impressive and contrasts with Tops-20 
where you have to configure these and (I believe) you do have some 
limits or some tables overflow.  I think the number of forks per job is 
limited by the job status block (JSB), which was never put into extended 
memory.  The number of forks is a hard limit and configured when 
building the monitor.  For PANDA, the system can accommodate a maximum 
of 320 forks.  I guess that is probably plenty for all but the most 
excessive hobbyist usage. This is what my typical development job looks 
like:

    @i fork
         Editor (1): Editor, Kept, HALT at 53206, 0:00:22.1
         SETNODE-Sources (3): Kept, HALT at 53206, 0:06:23.0
         Once-Source (4): Kept, HALT at 53206, 0:00:48.9
         STAR-Sources (5): Kept, HALT at 53206, 0:07:47.7
         EFTPSER-Sources (6): Kept, HALT at 53206, 0:00:01.9
         Monitor-DECnet-Sources (7): Kept, HALT at 53206, 0:00:10.1
         ALGOTS-Sources (12): Kept, HALT at 53206, 0:00:59.0
         DN60-Sources (13): Kept, HALT at 53206, 0:00:00.8
         BATCON-Sources (14): Kept, HALT at 53206, 0:00:15.3
         FAL-DAPLIB-Sources (15): Kept, HALT at 53206, 0:00:01.2
         PA1050-Sources (16): Kept, HALT at 53206, 0:03:40.5
         NETPTH-DECnet-Ping-Sources (17): Kept, HALT at 53206, 0:00:09.7
         DDT-Sources (21): Kept, HALT at 53206, 0:01:28.8
         Exec-Sources (22): Kept, HALT at 53206, 0:00:05.5
         LAT-Sources (23): Kept, HALT at 53206, 0:00:08.3
      => Monitor-TTY-Service (10): Kept, HALT at 53206, 0:00:04.5
         Kermit-Source (11): Kept, HALT at 53206, 0:03:25.4
         Monitor-Scheduler (20): Kept, HALT at 53206, 0:00:09.3
         Monitor-DTE-Driver (2): Kept, HALT at 53206, 0:00:07.1
         Monitor-NRT-Sources (24): Kept, HALT at 53206, 0:00:03.8
    @

At certain times of the year, using 20 forks to handle various source 
and editing might have gotten me a scolding, back in the day.  During 
the summer however, we went from 3 student DEC20's to one (CU20A) and 
the other two (CU20C and CUU20D) were handed over to staff for 
development and to get them off the staff machine (CU20B). I did get 
close to this one summer when I was putting Columbia's (extensive) 
modifications into the Tops-20 V6 field test.

> ------------------------------------------------------------------------
> On 11/12/21 6:12 PM, Johnny Billquist wrote:
>
> There is no hard limit on the number of logged in users in RSX. And no 
> hard limit on the number of running tasks either.
>
> Controlling lots of terminals from one process in RSX is easy. You do 
> need to have the terminals open, but the limit on devices accessed 
> from one task is 256. You don't need to have active I/Os to any 
> terminal in order to read from them, so it's actually very little 
> resources required. A little bit of memory, but that's it.
>
> I believe this was used out by customers in lots of places. I never 
> saw any really big ones, but I heard about 911 dispatch centers in the 
> US. But small scale solutions on the same principles were/are being 
> run that I know of...
>
>   Johnny
>> ------------------------------------------------------------------------
>> On 2021-11-12 21:01, Paul Koning wrote:
>>
>> RSTS has an API for that, allowing one program to control lots of 
>> terminals without having to open lots of individual files for each 
>> terminal.  It makes it possible to support 127 terminals, even though 
>> the number of logged-in users is limited to 63.
>>> ------------------------------------------------------------------------
>>> On Nov 11, 2021, at 6:49 PM, Johnny Billquist <bqt at softjar.se> wrote:
>>>
>>> RSX-11M-PLUS can have up to 256 terminals. However, I sortof doubt 
>>> much useful stuff would happen if you had that many users running 
>>> interactively.
>>>
>>> I think it was more used for systems where you had some clever 
>>> programs running that controlled lots of terminals.
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