> Of course, that doesn't tell you with certainty that the IRQ is in
> fact usable; some other device _could_ have generated an interrupt, or
> there could be a spurious interrupt on the line.

Also, it may be that sampling the register works, but toggling the CPU
interrupt line doesn't.   But this is pure speculation - the right
thing to do is try it out!   Would that I had time... :'(

          _MelloN_