Why do any tasks load Macbook Pro by 100+%?

Question

macbook

Good day.
I have a 2012 Mac Book Pro.
OS X 10.10
The computer, although not new, still worked perfectly until recently.
After the next update of OS X 10.10, it began to slow down fiercely, load averages does not fall below 2-3.
Moreover, it loads the percentage of any software, be it Mail or Skype, or just simply the Code Editor.
For the experiment, I installed 10.8 + I bought an SSD
Nothing has changed.
Now any program can start loading percents when working with it, while load averages rises to 10-12
. Of course, it is not possible to work with this.
I don’t even know what to do, the system is clean, but the same effect was on 10.10
Maybe someone came across?