If you mean ioapic pin 9, then it is hard to say, because there
is constant interrupt activity there. vmstat reports rate 11.
I tried hitting the power button repeatedly while watching
"vmstat -i 1" output, but couldn't see any change in the interrupt
rate. Nor was there change in any other interrupt rates.
Hmm, watching "systat vm 1" output, I do see a change in ioapic
pin 9 interrupt rate when I press the power button repeatedly.
It seems to never go above 10 normally, but when hitting the
power button the rate does go up. The sleep button (which is
behind a Fn + normal key) does not affect the interrupt rate on
pin 9.