VMS stability back in the day (was Re: NuTek Mac comes)

Paul Koning paulkoning at comcast.net
Sun Jul 17 09:47:58 CDT 2016

> On Jul 17, 2016, at 10:41 AM, Paul Koning <paulkoning at comcast.net> wrote:
> ...
> I suppose so.  Rumor had it that Phase I only existed on RSX, but it appears that there was a PDP-8 implementation as well.  Phase II was implemented on lots of DEC systems, from TOPS-10 to RT-11 to RSTS/E.

By the way: starting with Phase III, DEC adopted "one phase back" compatibility.  A Phase III node could talk to Phase II; a Phase IV node could talk to Phase III, all documented clearly in the specifications.  (Two phases back wasn't described or aimed for, though it is not that hard; my DECnet/Python does Phase IV but talks to Phase II.)

On the other hand, Phase II is not compatible with Phase I; the packet formats are significantly and it's clear that no attempt was made to deliver compatibility.  I don't know why not, or why that changed later.  (Before my time...)


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