CPU Utilization

I’m really confused about the “CPU Utilization” chart which is shown on the test result page since I found different interpretations of this chat in this forum:

  1. Some posts in this forum state that this is chart shows client side (browser) CPU utilization caused by javascript execution etc…:

https://www.webpagetest.org/forums/showthread.php?tid=256

  1. Other posts claim this this chart shows CPU utilization on the server:

https://www.webpagetest.org/forums/showthread.php?tid=977
http://www.webpagetest.org/forums/archive/index.php?thread-5529.html

Which of these interpretations is true? From my personal experience would opt for the second option since CPU Utilization varies a lot depending on test location.

Can someone please clearify?