Ultrix tape job is unkillable!

[Henry Spencer]

In article <17909 at glacier.STANFORD.EDU> jbn at glacier.UUCP (John B. Nagle) writes:
>      Lost interrupts tend to be more of a problem on systems with interrupts
>as edges rather than levels.  PDP11s and VAXen are in the former category, and
>Motorola M680x0 machines are in the latter.  On Motorola iron, and on the
>buses usually used with it, controllers raise an interrupt line when they
>want attention, and the interrupt will recur until the controller is made
>happy...

Can you explain where you got the idea that the PDP11 (I can't speak for
the VAX) does something different?  Believe me, having an interrupt recur
until the controller is happy is a well-known nuisance on the 11, and as
far as I know (I'm not intimate with the Unibus any more), the protocol
is entirely level-triggered.

The problem being discussed here is not an interrupt being missed, but no
interrupt coming in at all -- the software is waiting for an event that
may never occur if the tape drive is meddled with by humans.
-- 
"God willing, we will return." |     Henry Spencer at U of Toronto Zoology
-Eugene Cernan, the Moon, 1972 | uunet!attcan!utzoo!henry henry at zoo.toronto.edu