Activity Monitor #'s doesn't correspond

[proletarian]

I've bought an 27' iMac with Intel i7 just b4 x'mas last year. Everything seems pretty normal until a month ago. I've noticed that the #'s in the CPU section at the Activity Monitor(AM) doesn't add up to 100%. Even more strangely ,the "% idle" hovers at around 50% when applications (such as browser) are not in use . Once applications are in process , the #'s will be back to normal.
Apple has replaced the mother board along with the cpu, but the problem stays.
Apple here in Asia couldn't figure it out what went wrong. Despite the discrepancy in #'s , the machine seems to be working normal.
Does any 27' iMac users experience the same problem as I have???

 

[Aptmunich]

Have you selected "All processes" from the drop down list?
In any case, Idle % is supposed to be high - that's the amount of CPU time that is not busy. It's like saying "My car has 100% of its speed capacity available when it's standing still".

 

[proletarian]

On the contrary, I thought it was the other way around. My other two Mac Notebooks' (AM) do not experience the same discrepancies
Their #'s most of the time adds up to !00%.

 

[Aptmunich]

Believe what you want, this article has more info though:
What Is Activity Monitor (or How to Take Your Mac's Pulse) - O'Reilly Media

Or you could keep taking it to the genius bar...

 

[proletarian]

Thanks for reminding me of Genius Bar, I almost forgot this service.My gratitude to you. :Blushing: