Load ELRepo repository.

Install kernel-ml.

yum --enablerepo=elrepo-kernel install kernel-ml

Boot kernel 3.x. If you want, change default boot option in /etc/grub.conf

default=0

Install cpupower program.

yum install cpupowerutils

set governor

cpupower frequency-set --governor ondemand

Frequency info:

cpupower frequency-info

Make it reboot persistent, add a line in /etc/rc.local

cpupower frequency-set --governor ondemand