Take the 2-minute tour ×
Ask Different is a question and answer site for power users of Apple hardware and software. It's 100% free, no registration required.

I was trying to figure out why my Mountain Lion server was running slow, and I when I opened Activity Monitor this is what I saw:

activity monitor shot

Question 1: how am I getting >400% of CPU on the summed CPU column, when I only have 4 cores available?

Question 2: given that I have all this CPU activity, how am I getting these usage reports in the lower-left corner, esp. the 38% idle one?

share|improve this question
add comment

1 Answer

up vote 4 down vote accepted

Check this out for a previous post. But, adding a bit to that answer...

First - while you have 4 physical cores, you have hyperthreading active, which allows each core to serve as 2 virtual cores. This will give you a theoretical maximum CPU usage of 100% x 8, or 800%.

Second - the % reported in the activity monitor is showing total CPU% (so it won't exceed 100%). Looking at the CPU numbers in your table, you're using a bit more than 485% out of the maximum of 800%. 485/800 is about 60%, which is your total usage reflected here...

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.