In article ,
peter_notthis@byron.digitalvax.com says...
> Hello,
>
> I ran into this a couple of years ago and got it working somehow then, not
> sure how, but now it show's up again when I attempt to save all RL02-disk
> paks on a RA92 booted MicroVAX 3900.
>
> The systemdisk becomes unavailable, during RL02 activity and won't show up
> again until all has been power cycled, from the console the RA92 show's as
> "-?"
>
> I guess it some kind of conflict between the controllers but it's strange
> that it doesn't show up earlier then.
>
> It's VMS version 6.2 and unit's are DUB0 (RA92) and DLA0 (RL02), there are
> also RD54's as DUA0...2.
>
> ^P.Lj

I would suspect some kind of bus configuration problem. Possibly one
controller is stealing bus grants intended for the other and starving
it.

It sounds like you have at least an RQDX* (RD54s), a KDA50 (RA92) and
an RLV22(?) for the RL02. Make sure they are in the right order on
the bus (the uVAX 3900 Owner's or Maintenance Manual should have
configuration rules), and the controllers have the right addresses
and interrupt vectors (MCR SYSGEN CONFIGURE and/or the console
configuration utility should help here. DGAS Qbus and serpentine :-)

One a Unibus, if some device had a broken grant or NPR continuity
circuit, I think you could get similar problems, but I don't think
the same applies to Qbus.

I know this is pretty vague, but I hope it helps!

--
John