nexus stray intr message (4.2bsd)

[Steven Bellovin]

When I attempt to talk to a Datakit VCS (tm) via DR11-C on a VAX-11/785,
I get "nexus stray intr ipl15" messages every few seconds, at about the
rate of the keepalive messages between the host and the switch.  The
same code works fine on some 750s I've tried it on.

Now -- if I read my VAX hardware manuals and the 4.2bsd code correctly,
such messages "shouldn't happen".  Even if the device hooked to the DR11-C
is giving too brief an interrupt request signal, I should see a UNIBUS
zero vector, not a stray nexus interrupt.  Is this (another) known oddity
of 780 UNIBUSen?  What, if anything, should be tinkered with on the Datakit
end to make the problem go away?  Or should I get a new DR11-Cor UBA?  I've
seen similar messages, though with much lower frequency, on other 11/780s
and 11/785s with Datakit hookups; for one of them, though, it isn't clear
if the message is from Datakit's DR11-C or another peripheral's.

Please reply by mail.

		--Steve Bellovin
		{ucbvax,ihnp4,allegra, most of BTL}!ulysses!smb