Hello.
I'm using the latest image from https://www.armbian.com/rock64/ installed today.
As description say, it is possible to overclock the board to 1.5ghz, but it didn't work.
root@rock64:~# cat /sys/devices/system/cpu/cpu{0,1,2,3}/cpufreq/scaling_available_frequencies
408000 600000 816000 1008000 1200000 1296000
408000 600000 816000 1008000 1200000 1296000
408000 600000 816000 1008000 1200000 1296000
408000 600000 816000 1008000 1200000 1296000