DECNet for Pro 300 series boxes

Paul Koning paulkoning at
Mon May 17 19:43:32 CDT 2021

> On May 17, 2021, at 8:14 PM, Bill Degnan via cctalk <cctalk at> wrote:
> ...
> Maybe I am misunderstanding, but why would the pro be anything but more decnet-able?
> Bill

I'm not sure what you mean.  A Pro is a PDP-11 so it could do many DECnet things, especially the Pro 380 since it has more memory and a faster processor.  But it has two limitations compared to most other PDP-11s.

One is the I/O.  It comes stock with a single USART (the comm port) that, with effort, can be made to work reasonably well at 9600 baud.  At 19,200 it can't keep up, at least not with the RSTS terminal driver.  Perhaps that could be optimized.  

There are two comms option cards: the DECNA Ethernet, and the 3CA quad UART (a very obscure device).  The quad UART has a better FIFO than the USART so it's happy at 9600.  Just like the comm port, you're looking at DDCMP in software with those.  The CNA is a 10 Mb/s Ethernet (half duplex) device, using the worst Ethernet NIC chip in the history of mankind.  But it supposedly does work (I haven't done so yet).

So while you could build a router, it wouldn't have much of a suite of comm links.

The other limitation is the software.  DEC only supplied P/OS, RT-11, and Ultrix (or was that some other Unix?  I forgot, they changed plans in the middle of field test of one of them).  Of those, P/OS comes with DECnet, which is the one John Forecast was talking about.  Given that the version that was shipped is (apparently) end node only, that's what you're stuck with.  RT-11 for Pro does not as far as I know, and in any case RT-11 only ever did endnodes.  I have no idea about the Unix.  

Then there is RSTS, which can do all this (except, not yet, the DECNA), but I only ever released the more limited 9.6 version internally and still haven't managed to figure out a sane way to make the current (10.1 based) one available to the community.


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