I read it in an update of my favorite distro DietPi and didn't know this option.
If you add to /boot/config.txt the next option:
will force the CPU to a higher frequency at startup for a few seconds to improve the time it takes to boot. It can be set at dietpi-config > Performance Options > ARM Initial Turbo if you prefer.
I advise you to read the following link, especially if you use some kind of overclock.