Mysql kill CPU

Hi, since my site began to have more visits began to have more problems, the site has several queryes, but the strange thing was that 500-600 users (online at same time) worked well, 700 cpu fired.

I have a dedicated server:

RAM: 2x SM 8GB DDR3 1600MHz 2Rx8 ECC/Unbuffered

But i upgrade now to
Processor: Intel Xeon E3-1241v3
RAM: 2x SM 8GB DDR3 1600MHz 2Rx8 ECC/Unbuffered

I use ispManager, mysql 5.6, with php 5.3

max connections on nginx 1500

This is the CPU use now:
http://s7.postimg.org/axtxuwssr/Capturar.jpg

Now the max is 40% in a day, but you can see that he go to 70% some times.
Mysql is consuming 100-200% of cpu

Is mysql? nginx? server? config?

Help Me please, thank you

Hello,
Please check following things:

  1. turn off persistent connections
  2. double check your MySQL users