Steve Baldwin wrote:

> No, it's a different solution but with a similar amount of technical
> backup - ie. "This seemed to work"..."I vaguely recall"...etc. :-)

  No, I suspect it«s likely to be a different solution with the same
effect.  The sending of a non-specific EOI to the secondary controller
may cause it to clear and then re-assert its output IRQ before the
primary is ready to see it (and this assuming the actual calling IRQ has
in fact been cleared).

  If however, the primary is cleared first, it is able to respond to the
second call from the secondary and the subsequent interrupt will be
honoured.
--
  Cheers,
        Paul B.