[HECnet] Multinet alternatives ...

[Thomas DeBellis]

Bob,

I can't speak to Tops-10 with much authority any more, but I believe 
that in order to get the Phase IV support in Tops-20, you have to be 
running version 5 or, more likely, version 6 or 7.  All of these require 
a KL class machine due to the requirement for extended addressing.

When I last checked, SIMH was 'only' capable of emulating the KA, KI and 
KS PDP-10 processors, none of which will support more than a 256K 
virtual code space.  I believe MRC was able to fit version 5 into the 
KS, but those sources are not currently available (in fact, they may be 
lost).

But, as he frequently said, the KL is only 'reasonable' processor as it 
has 23 bit virtual address space, which puts you into the megabyte 
range.  Later processors have a 30 bit address space, which gets you a 
gigabyte address space.  That's plenty of space unless you are doing 
multimedia.

Thus, your only reasonable alternative is the KLH10 emulator which will 
do Phase IV over Ethernet and the CI.  It is superior to SIMH in certain 
respects as it has a multi-threaded model where devices can and do run 
concurrently to the processors.  However, certain things remain either 
unimplemented (such as the CI) or minimally implemented.

This is relevant because the DECSYSTEM-20 architecture had a KL 
surrounded by up to four PDP-11's, one of which ran the DECnet code 
(branded a DN20).  These handled synchronous communications and did the 
DDCMP.  The problem is that the interface between the KL and the PDP-11, 
called a DTE for Data-Ten-to-Eleven, implementation is minimal.  This 
would need to be fleshed out both for KLH10 and SIMH and some sort of 
data path agreed to (one assumes UDP).  Then you could boot the DN20 
code (I forget the internal name, maybe MCB) and have DDCMP from Tops-20.

Sounds like fun, but an extensive amount of it...

         --T

On 2/25/20 10:40 AM, Robert Armstrong wrote:
>
> -----Original Message-----
> From: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Paul Koning
> Sent: Tuesday, February 25, 2020 6:53 AM
> To: hecnet at update.uu.se
> Subject: Re: [HECnet] Multinet alternatives ...
>
>
>
>> Paul Koning [paulkoning at comcast.net] wrote:
>> There was, but I think Python recently dropped VMS support due to lack of a maintainer.
>    Dropped VMS or dropped VAX?  There was a Python for AXP (although I don't know if it's still supported) but I don't think there was for VAX.
>
>    How do people who use your router typically run it?  Do they run it on Linux?
>
>> TOPS-10 is Phase IV, right?  Any of the common DECnet implementations should talk to that.
>    TOPS-10 v7.04 (or maybe 7.05) is Phase IV.  That's good news - I've wanted to set up a TOPS-10 simulation, but running a simh780 just to route DECnet for the DMR on TOPS-10 was not attractive.
>
>    I'd rather have TOPS-20 but as you say TOPS-20 on simh with networking is not very practical.
>
> Bob
>
>