[HECnet] Another TOPS-10 DECnet problem

[Paul Koning]

> 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.

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.

A variation on this theme (with a specialized bulk data DMA service) was used by the inhouse APT tool to drive manufacturing test setups.

> But PDP-11 systems were/are pretty capable, considering some of the limitations... And they are still being used in some places, which I find pretty nice. And of course, I continue whack at them when I get a chance. The combination of TCP/IP, web servers, and stuff like Datatrieve makes it look almost like some modern stack of tools. I'm having blast nearly every day. I just wish I could locate the sources of the layered products...

Another example of a large configuration is Typeset-11 (TMS-11).  I don't remember exactly what the terminal limit is on that, but I'm fairly sure it was at least 64.  TMS-11 systems also do a form of clustering, with up to 4 nodes (at least -- that's the max I remember) with dynamic routing dating back to before DECnet did that.  Part of the reason such a large setup worked is that the terminals are all block-editing terminals, with the main editing work done on VT-71 terminals where you download a file, edit it entirely in the terminal (thanks to an 11/23 inside) and send back the result.

Typeset-11 had some rather odd I/O: 6-bit UARTs carrying data streams from wire service feeds like Associated Press, custom interfaces to typesetting machines (this is before PostScript), multipoint BiSync over DL-11/E interfaces to connect to Harris 2200 display ad editing terminals, ...

	paul