在cmd line的模式下來超頻 on raspberry

sudo vi /boot/config.txt

In this file, you’ll want to add the following two lines:

arm_freq=800
sdram_freq=500

reboot ....and check this frequency by

vcgencmd get_config arm_freq

and it should be

arm_freq=800

Maybe you could use

sudo raspi-config

Again to check it, you can type in

vcgencmd get_config arm_freq

and it should say:

arm_freq=800

You can also check more options by typing:

vcgencmd get_config int

And it should look like this:

arm_freq=800
core_freq=250
sdram_freq=500
disable_overscan=1
boot_delay=1
temp_limit=85

Enjoy! 

Reference : https://www.jeremymorgan.com/tutorials/raspberry-pi/how-to-overclock-raspberry-pi/