When connecting a second external monitor kernel\_task spikes to 600%+. This makes the computer unusable.

Before Yosemite, this worked fine with 3 monitors.

Here are the specifics: 

* When I connect one monitor to either DP or HDMI things work fine.
* When I connect a second monitor with either DP or HDMI kernel\_task spikes.
* When I disconnect either the DP or HDMI *sometimes* the kernel\_task rapidly returns to normal levels.
* When I disconnect all monitors the kernel\_task rapid returns to normal levels. (In Activity Monitor goto `View > Update Frequency > Very Often` and as soon as you disconnect the monitors, you will get lots of rapid updates to the UI).
* Occasionally when plugging in two monitors it works (DP or HDMI) but the 3rd causes an immediate spike. After this happens, all monitors must be removed for it to return to normal. *Sometimes* removing all but one will fix it.
* Sometimes when I plug all 3 in it takes 3 mins+ for it to occur.

What I have tried:

* Resetting NVRAM.
* Resetting SMC.
* Attempting the above scenario with power adapter plugged in and running on battery.
* Disabling "Automatic Graphics Switching" in Energy Saver.
* Using integrated graphics by using `sudo pmset -c gpuswitch 0`

*NOTE: When trying some of these things sometimes it takes 1min to happen.*

System config:

I am running a MacBook Pro Retina 2.7Ghz i7 (Macbook10,1 / Mid 2012) running Yosemite 10.10.1.

I have 3 external monitors (Dell 2415H) with 2 connected by Display Port and 1 with the HDMI.

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I think the issue has to do with power management. Whenever my CPU hits 58 degrees it seems to occur. I just left my 3 monitors plugged in for 5+ mins and it didn't happen. But when I started searching using Chrome it immediately happened.

Looks like a good fix here: <http://www.rdoxenham.com/?p=259>