Open up a terminal window:
$ sudo apt update && sudo apt upgrade && sudo rpi-update && sudo reboot
After restarting:
$ sudo nano /boot/config.txt
Scroll down to the very end and insert
over_voltage=4
arm_freq=2000
You can also overclock the GPU if needed:
gpu_freq=600
Ctrl+X and Y to save and run:
$ sudo reboot
After restarting, this will display the current CPU speed in real time:
$ watch -n1 vcgencmd measure_clock arm
CPU Benchmarking
$ sysbench --num-threads=8 --test=cpu --cpu-max-prime=2000 run
If not installed:
$ curl -s https://packagecloud.io/install/repositories/akopytov/sysbench/script.deb.sh | sudo bash
$ sudo apt -y install sysbench