I noticed today a higher
kernel_task CPU usage when playing audio through Thunderbolt Display from my Macbook Pro (early 2011) on OS X Yosemite. Although the CPU usage is not very high (15 - 20%), it certainly gets the fans spinning fast enough to get my attention. I would not expect this as a normal behaviour.
I've tried Spotify, iTunes and playing a YouTube video in Safari and got the same results. Here is an example when playing a song from iTunes through the internal speakers (I get the same values with headphones):
And here is the
kernel_task usage when playing the same song through my Thunderbolt Display:
I have tried both SMC and PRAM resets, but to no avail. What could be causing this? Does anyone else experience this behaviour?