[Simh] Issue #731 - simh PDP11 RSX11M-PLUS Unibus 11/94 system with 2 DEUNA ethernet device XUB not working

[Paul Koning]

I haven't tried 2 UNA at all, and don't know RSX, but one thing to watch out for: don't put two Ethernet interfaces on the same LAN if you're running DECnet (Phase IV).  The reason is that they will both set the same Ethernet address, from the DECnet node address, so you have a duplicate address condition.  If both are connected to the same LAN segment this will make for a mess; if they are connected to different segments of a switched Ethernet then many packets will be lost as the switches keep changing their mind about where that address is located.

	paul

> On Jul 26, 2019, at 11:26 PM, Geoff Conway <gconway at bigpond.net.au> wrote:
> 
> Hi All,
>  
> I have just raised an Issue in simh #731 where when recent testing with a simh PDP11/94 Unibus system with 2 DEUNA interfaces it was found that device XUB did not initialize. Device XU worked normally. I have not yet been able have XUB start fully – no matter what CSR/VEC combination I have tried. I believe the current CSR & VEC are correct as they have been assigned – just that there appears some internal disconnect within the XU driver where XUB channel just does not do anything.
>  
> In the equivalent simh PDP11/93 Qbus system with 2 DEQNA both XQ, XQB worked normally.
>  
> The details of the actual system configuration is in the Issues log. With the absence of any messages from XUB it appears to be dead in the water – although when running the simh environment with DEBUG enabled in both XU, XUB I found that XUB stayed in xu_process_local() while the XU device had a lot of activity – which was expected since XU was working normally whereas XUB was not.
> Unfortunately as I am not familiar with the XU driver code I have not been able to determine why the xub interface is not initializing correctly.
>  
> Regards
>  
> Geoff
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